--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mercurial/interfaces/repository.py	Sun Aug 18 00:45:33 2019 +0300
@@ -0,0 +1,1877 @@
+# repository.py - Interfaces and base classes for repositories and peers.
+#
+# Copyright 2017 Gregory Szorc <gregory.szorc@gmail.com>
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+from __future__ import absolute_import
+
+from ..i18n import _
+from .. import (
+    error,
+)
+from ..utils import (
+    interfaceutil,
+)
+
+# When narrowing is finalized and no longer subject to format changes,
+# we should move this to just "narrow" or similar.
+NARROW_REQUIREMENT = 'narrowhg-experimental'
+
+# Local repository feature string.
+
+# Revlogs are being used for file storage.
+REPO_FEATURE_REVLOG_FILE_STORAGE = b'revlogfilestorage'
+# The storage part of the repository is shared from an external source.
+REPO_FEATURE_SHARED_STORAGE = b'sharedstore'
+# LFS supported for backing file storage.
+REPO_FEATURE_LFS = b'lfs'
+# Repository supports being stream cloned.
+REPO_FEATURE_STREAM_CLONE = b'streamclone'
+# Files storage may lack data for all ancestors.
+REPO_FEATURE_SHALLOW_FILE_STORAGE = b'shallowfilestorage'
+
+REVISION_FLAG_CENSORED = 1 << 15
+REVISION_FLAG_ELLIPSIS = 1 << 14
+REVISION_FLAG_EXTSTORED = 1 << 13
+
+REVISION_FLAGS_KNOWN = (
+    REVISION_FLAG_CENSORED | REVISION_FLAG_ELLIPSIS | REVISION_FLAG_EXTSTORED)
+
+CG_DELTAMODE_STD = b'default'
+CG_DELTAMODE_PREV = b'previous'
+CG_DELTAMODE_FULL = b'fulltext'
+CG_DELTAMODE_P1 = b'p1'
+
+class ipeerconnection(interfaceutil.Interface):
+    """Represents a "connection" to a repository.
+
+    This is the base interface for representing a connection to a repository.
+    It holds basic properties and methods applicable to all peer types.
+
+    This is not a complete interface definition and should not be used
+    outside of this module.
+    """
+    ui = interfaceutil.Attribute("""ui.ui instance""")
+
+    def url():
+        """Returns a URL string representing this peer.
+
+        Currently, implementations expose the raw URL used to construct the
+        instance. It may contain credentials as part of the URL. The
+        expectations of the value aren't well-defined and this could lead to
+        data leakage.
+
+        TODO audit/clean consumers and more clearly define the contents of this
+        value.
+        """
+
+    def local():
+        """Returns a local repository instance.
+
+        If the peer represents a local repository, returns an object that
+        can be used to interface with it. Otherwise returns ``None``.
+        """
+
+    def peer():
+        """Returns an object conforming to this interface.
+
+        Most implementations will ``return self``.
+        """
+
+    def canpush():
+        """Returns a boolean indicating if this peer can be pushed to."""
+
+    def close():
+        """Close the connection to this peer.
+
+        This is called when the peer will no longer be used. Resources
+        associated with the peer should be cleaned up.
+        """
+
+class ipeercapabilities(interfaceutil.Interface):
+    """Peer sub-interface related to capabilities."""
+
+    def capable(name):
+        """Determine support for a named capability.
+
+        Returns ``False`` if capability not supported.
+
+        Returns ``True`` if boolean capability is supported. Returns a string
+        if capability support is non-boolean.
+
+        Capability strings may or may not map to wire protocol capabilities.
+        """
+
+    def requirecap(name, purpose):
+        """Require a capability to be present.
+
+        Raises a ``CapabilityError`` if the capability isn't present.
+        """
+
+class ipeercommands(interfaceutil.Interface):
+    """Client-side interface for communicating over the wire protocol.
+
+    This interface is used as a gateway to the Mercurial wire protocol.
+    methods commonly call wire protocol commands of the same name.
+    """
+
+    def branchmap():
+        """Obtain heads in named branches.
+
+        Returns a dict mapping branch name to an iterable of nodes that are
+        heads on that branch.
+        """
+
+    def capabilities():
+        """Obtain capabilities of the peer.
+
+        Returns a set of string capabilities.
+        """
+
+    def clonebundles():
+        """Obtains the clone bundles manifest for the repo.
+
+        Returns the manifest as unparsed bytes.
+        """
+
+    def debugwireargs(one, two, three=None, four=None, five=None):
+        """Used to facilitate debugging of arguments passed over the wire."""
+
+    def getbundle(source, **kwargs):
+        """Obtain remote repository data as a bundle.
+
+        This command is how the bulk of repository data is transferred from
+        the peer to the local repository
+
+        Returns a generator of bundle data.
+        """
+
+    def heads():
+        """Determine all known head revisions in the peer.
+
+        Returns an iterable of binary nodes.
+        """
+
+    def known(nodes):
+        """Determine whether multiple nodes are known.
+
+        Accepts an iterable of nodes whose presence to check for.
+
+        Returns an iterable of booleans indicating of the corresponding node
+        at that index is known to the peer.
+        """
+
+    def listkeys(namespace):
+        """Obtain all keys in a pushkey namespace.
+
+        Returns an iterable of key names.
+        """
+
+    def lookup(key):
+        """Resolve a value to a known revision.
+
+        Returns a binary node of the resolved revision on success.
+        """
+
+    def pushkey(namespace, key, old, new):
+        """Set a value using the ``pushkey`` protocol.
+
+        Arguments correspond to the pushkey namespace and key to operate on and
+        the old and new values for that key.
+
+        Returns a string with the peer result. The value inside varies by the
+        namespace.
+        """
+
+    def stream_out():
+        """Obtain streaming clone data.
+
+        Successful result should be a generator of data chunks.
+        """
+
+    def unbundle(bundle, heads, url):
+        """Transfer repository data to the peer.
+
+        This is how the bulk of data during a push is transferred.
+
+        Returns the integer number of heads added to the peer.
+        """
+
+class ipeerlegacycommands(interfaceutil.Interface):
+    """Interface for implementing support for legacy wire protocol commands.
+
+    Wire protocol commands transition to legacy status when they are no longer
+    used by modern clients. To facilitate identifying which commands are
+    legacy, the interfaces are split.
+    """
+
+    def between(pairs):
+        """Obtain nodes between pairs of nodes.
+
+        ``pairs`` is an iterable of node pairs.
+
+        Returns an iterable of iterables of nodes corresponding to each
+        requested pair.
+        """
+
+    def branches(nodes):
+        """Obtain ancestor changesets of specific nodes back to a branch point.
+
+        For each requested node, the peer finds the first ancestor node that is
+        a DAG root or is a merge.
+
+        Returns an iterable of iterables with the resolved values for each node.
+        """
+
+    def changegroup(nodes, source):
+        """Obtain a changegroup with data for descendants of specified nodes."""
+
+    def changegroupsubset(bases, heads, source):
+        pass
+
+class ipeercommandexecutor(interfaceutil.Interface):
+    """Represents a mechanism to execute remote commands.
+
+    This is the primary interface for requesting that wire protocol commands
+    be executed. Instances of this interface are active in a context manager
+    and have a well-defined lifetime. When the context manager exits, all
+    outstanding requests are waited on.
+    """
+
+    def callcommand(name, args):
+        """Request that a named command be executed.
+
+        Receives the command name and a dictionary of command arguments.
+
+        Returns a ``concurrent.futures.Future`` that will resolve to the
+        result of that command request. That exact value is left up to
+        the implementation and possibly varies by command.
+
+        Not all commands can coexist with other commands in an executor
+        instance: it depends on the underlying wire protocol transport being
+        used and the command itself.
+
+        Implementations MAY call ``sendcommands()`` automatically if the
+        requested command can not coexist with other commands in this executor.
+
+        Implementations MAY call ``sendcommands()`` automatically when the
+        future's ``result()`` is called. So, consumers using multiple
+        commands with an executor MUST ensure that ``result()`` is not called
+        until all command requests have been issued.
+        """
+
+    def sendcommands():
+        """Trigger submission of queued command requests.
+
+        Not all transports submit commands as soon as they are requested to
+        run. When called, this method forces queued command requests to be
+        issued. It will no-op if all commands have already been sent.
+
+        When called, no more new commands may be issued with this executor.
+        """
+
+    def close():
+        """Signal that this command request is finished.
+
+        When called, no more new commands may be issued. All outstanding
+        commands that have previously been issued are waited on before
+        returning. This not only includes waiting for the futures to resolve,
+        but also waiting for all response data to arrive. In other words,
+        calling this waits for all on-wire state for issued command requests
+        to finish.
+
+        When used as a context manager, this method is called when exiting the
+        context manager.
+
+        This method may call ``sendcommands()`` if there are buffered commands.
+        """
+
+class ipeerrequests(interfaceutil.Interface):
+    """Interface for executing commands on a peer."""
+
+    limitedarguments = interfaceutil.Attribute(
+        """True if the peer cannot receive large argument value for commands."""
+    )
+
+    def commandexecutor():
+        """A context manager that resolves to an ipeercommandexecutor.
+
+        The object this resolves to can be used to issue command requests
+        to the peer.
+
+        Callers should call its ``callcommand`` method to issue command
+        requests.
+
+        A new executor should be obtained for each distinct set of commands
+        (possibly just a single command) that the consumer wants to execute
+        as part of a single operation or round trip. This is because some
+        peers are half-duplex and/or don't support persistent connections.
+        e.g. in the case of HTTP peers, commands sent to an executor represent
+        a single HTTP request. While some peers may support multiple command
+        sends over the wire per executor, consumers need to code to the least
+        capable peer. So it should be assumed that command executors buffer
+        called commands until they are told to send them and that each
+        command executor could result in a new connection or wire-level request
+        being issued.
+        """
+
+class ipeerbase(ipeerconnection, ipeercapabilities, ipeerrequests):
+    """Unified interface for peer repositories.
+
+    All peer instances must conform to this interface.
+    """
+
+class ipeerv2(ipeerconnection, ipeercapabilities, ipeerrequests):
+    """Unified peer interface for wire protocol version 2 peers."""
+
+    apidescriptor = interfaceutil.Attribute(
+        """Data structure holding description of server API.""")
+
+@interfaceutil.implementer(ipeerbase)
+class peer(object):
+    """Base class for peer repositories."""
+
+    limitedarguments = False
+
+    def capable(self, name):
+        caps = self.capabilities()
+        if name in caps:
+            return True
+
+        name = '%s=' % name
+        for cap in caps:
+            if cap.startswith(name):
+                return cap[len(name):]
+
+        return False
+
+    def requirecap(self, name, purpose):
+        if self.capable(name):
+            return
+
+        raise error.CapabilityError(
+            _('cannot %s; remote repository does not support the '
+              '\'%s\' capability') % (purpose, name))
+
+class iverifyproblem(interfaceutil.Interface):
+    """Represents a problem with the integrity of the repository.
+
+    Instances of this interface are emitted to describe an integrity issue
+    with a repository (e.g. corrupt storage, missing data, etc).
+
+    Instances are essentially messages associated with severity.
+    """
+    warning = interfaceutil.Attribute(
+        """Message indicating a non-fatal problem.""")
+
+    error = interfaceutil.Attribute(
+        """Message indicating a fatal problem.""")
+
+    node = interfaceutil.Attribute(
+        """Revision encountering the problem.
+
+        ``None`` means the problem doesn't apply to a single revision.
+        """)
+
+class irevisiondelta(interfaceutil.Interface):
+    """Represents a delta between one revision and another.
+
+    Instances convey enough information to allow a revision to be exchanged
+    with another repository.
+
+    Instances represent the fulltext revision data or a delta against
+    another revision. Therefore the ``revision`` and ``delta`` attributes
+    are mutually exclusive.
+
+    Typically used for changegroup generation.
+    """
+
+    node = interfaceutil.Attribute(
+        """20 byte node of this revision.""")
+
+    p1node = interfaceutil.Attribute(
+        """20 byte node of 1st parent of this revision.""")
+
+    p2node = interfaceutil.Attribute(
+        """20 byte node of 2nd parent of this revision.""")
+
+    linknode = interfaceutil.Attribute(
+        """20 byte node of the changelog revision this node is linked to.""")
+
+    flags = interfaceutil.Attribute(
+        """2 bytes of integer flags that apply to this revision.
+
+        This is a bitwise composition of the ``REVISION_FLAG_*`` constants.
+        """)
+
+    basenode = interfaceutil.Attribute(
+        """20 byte node of the revision this data is a delta against.
+
+        ``nullid`` indicates that the revision is a full revision and not
+        a delta.
+        """)
+
+    baserevisionsize = interfaceutil.Attribute(
+        """Size of base revision this delta is against.
+
+        May be ``None`` if ``basenode`` is ``nullid``.
+        """)
+
+    revision = interfaceutil.Attribute(
+        """Raw fulltext of revision data for this node.""")
+
+    delta = interfaceutil.Attribute(
+        """Delta between ``basenode`` and ``node``.
+
+        Stored in the bdiff delta format.
+        """)
+
+class ifilerevisionssequence(interfaceutil.Interface):
+    """Contains index data for all revisions of a file.
+
+    Types implementing this behave like lists of tuples. The index
+    in the list corresponds to the revision number. The values contain
+    index metadata.
+
+    The *null* revision (revision number -1) is always the last item
+    in the index.
+    """
+
+    def __len__():
+        """The total number of revisions."""
+
+    def __getitem__(rev):
+        """Returns the object having a specific revision number.
+
+        Returns an 8-tuple with the following fields:
+
+        offset+flags
+           Contains the offset and flags for the revision. 64-bit unsigned
+           integer where first 6 bytes are the offset and the next 2 bytes
+           are flags. The offset can be 0 if it is not used by the store.
+        compressed size
+            Size of the revision data in the store. It can be 0 if it isn't
+            needed by the store.
+        uncompressed size
+            Fulltext size. It can be 0 if it isn't needed by the store.
+        base revision
+            Revision number of revision the delta for storage is encoded
+            against. -1 indicates not encoded against a base revision.
+        link revision
+            Revision number of changelog revision this entry is related to.
+        p1 revision
+            Revision number of 1st parent. -1 if no 1st parent.
+        p2 revision
+            Revision number of 2nd parent. -1 if no 1st parent.
+        node
+            Binary node value for this revision number.
+
+        Negative values should index off the end of the sequence. ``-1``
+        should return the null revision. ``-2`` should return the most
+        recent revision.
+        """
+
+    def __contains__(rev):
+        """Whether a revision number exists."""
+
+    def insert(self, i, entry):
+        """Add an item to the index at specific revision."""
+
+class ifileindex(interfaceutil.Interface):
+    """Storage interface for index data of a single file.
+
+    File storage data is divided into index metadata and data storage.
+    This interface defines the index portion of the interface.
+
+    The index logically consists of:
+
+    * A mapping between revision numbers and nodes.
+    * DAG data (storing and querying the relationship between nodes).
+    * Metadata to facilitate storage.
+    """
+    def __len__():
+        """Obtain the number of revisions stored for this file."""
+
+    def __iter__():
+        """Iterate over revision numbers for this file."""
+
+    def hasnode(node):
+        """Returns a bool indicating if a node is known to this store.
+
+        Implementations must only return True for full, binary node values:
+        hex nodes, revision numbers, and partial node matches must be
+        rejected.
+
+        The null node is never present.
+        """
+
+    def revs(start=0, stop=None):
+        """Iterate over revision numbers for this file, with control."""
+
+    def parents(node):
+        """Returns a 2-tuple of parent nodes for a revision.
+
+        Values will be ``nullid`` if the parent is empty.
+        """
+
+    def parentrevs(rev):
+        """Like parents() but operates on revision numbers."""
+
+    def rev(node):
+        """Obtain the revision number given a node.
+
+        Raises ``error.LookupError`` if the node is not known.
+        """
+
+    def node(rev):
+        """Obtain the node value given a revision number.
+
+        Raises ``IndexError`` if the node is not known.
+        """
+
+    def lookup(node):
+        """Attempt to resolve a value to a node.
+
+        Value can be a binary node, hex node, revision number, or a string
+        that can be converted to an integer.
+
+        Raises ``error.LookupError`` if a node could not be resolved.
+        """
+
+    def linkrev(rev):
+        """Obtain the changeset revision number a revision is linked to."""
+
+    def iscensored(rev):
+        """Return whether a revision's content has been censored."""
+
+    def commonancestorsheads(node1, node2):
+        """Obtain an iterable of nodes containing heads of common ancestors.
+
+        See ``ancestor.commonancestorsheads()``.
+        """
+
+    def descendants(revs):
+        """Obtain descendant revision numbers for a set of revision numbers.
+
+        If ``nullrev`` is in the set, this is equivalent to ``revs()``.
+        """
+
+    def heads(start=None, stop=None):
+        """Obtain a list of nodes that are DAG heads, with control.
+
+        The set of revisions examined can be limited by specifying
+        ``start`` and ``stop``. ``start`` is a node. ``stop`` is an
+        iterable of nodes. DAG traversal starts at earlier revision
+        ``start`` and iterates forward until any node in ``stop`` is
+        encountered.
+        """
+
+    def children(node):
+        """Obtain nodes that are children of a node.
+
+        Returns a list of nodes.
+        """
+
+class ifiledata(interfaceutil.Interface):
+    """Storage interface for data storage of a specific file.
+
+    This complements ``ifileindex`` and provides an interface for accessing
+    data for a tracked file.
+    """
+    def size(rev):
+        """Obtain the fulltext size of file data.
+
+        Any metadata is excluded from size measurements.
+        """
+
+    def revision(node, raw=False):
+        """"Obtain fulltext data for a node.
+
+        By default, any storage transformations are applied before the data
+        is returned. If ``raw`` is True, non-raw storage transformations
+        are not applied.
+
+        The fulltext data may contain a header containing metadata. Most
+        consumers should use ``read()`` to obtain the actual file data.
+        """
+
+    def rawdata(node):
+        """Obtain raw data for a node.
+        """
+
+    def read(node):
+        """Resolve file fulltext data.
+
+        This is similar to ``revision()`` except any metadata in the data
+        headers is stripped.
+        """
+
+    def renamed(node):
+        """Obtain copy metadata for a node.
+
+        Returns ``False`` if no copy metadata is stored or a 2-tuple of
+        (path, node) from which this revision was copied.
+        """
+
+    def cmp(node, fulltext):
+        """Compare fulltext to another revision.
+
+        Returns True if the fulltext is different from what is stored.
+
+        This takes copy metadata into account.
+
+        TODO better document the copy metadata and censoring logic.
+        """
+
+    def emitrevisions(nodes,
+                      nodesorder=None,
+                      revisiondata=False,
+                      assumehaveparentrevisions=False,
+                      deltamode=CG_DELTAMODE_STD):
+        """Produce ``irevisiondelta`` for revisions.
+
+        Given an iterable of nodes, emits objects conforming to the
+        ``irevisiondelta`` interface that describe revisions in storage.
+
+        This method is a generator.
+
+        The input nodes may be unordered. Implementations must ensure that a
+        node's parents are emitted before the node itself. Transitively, this
+        means that a node may only be emitted once all its ancestors in
+        ``nodes`` have also been emitted.
+
+        By default, emits "index" data (the ``node``, ``p1node``, and
+        ``p2node`` attributes). If ``revisiondata`` is set, revision data
+        will also be present on the emitted objects.
+
+        With default argument values, implementations can choose to emit
+        either fulltext revision data or a delta. When emitting deltas,
+        implementations must consider whether the delta's base revision
+        fulltext is available to the receiver.
+
+        The base revision fulltext is guaranteed to be available if any of
+        the following are met:
+
+        * Its fulltext revision was emitted by this method call.
+        * A delta for that revision was emitted by this method call.
+        * ``assumehaveparentrevisions`` is True and the base revision is a
+          parent of the node.
+
+        ``nodesorder`` can be used to control the order that revisions are
+        emitted. By default, revisions can be reordered as long as they are
+        in DAG topological order (see above). If the value is ``nodes``,
+        the iteration order from ``nodes`` should be used. If the value is
+        ``storage``, then the native order from the backing storage layer
+        is used. (Not all storage layers will have strong ordering and behavior
+        of this mode is storage-dependent.) ``nodes`` ordering can force
+        revisions to be emitted before their ancestors, so consumers should
+        use it with care.
+
+        The ``linknode`` attribute on the returned ``irevisiondelta`` may not
+        be set and it is the caller's responsibility to resolve it, if needed.
+
+        If ``deltamode`` is CG_DELTAMODE_PREV and revision data is requested,
+        all revision data should be emitted as deltas against the revision
+        emitted just prior. The initial revision should be a delta against its
+        1st parent.
+        """
+
+class ifilemutation(interfaceutil.Interface):
+    """Storage interface for mutation events of a tracked file."""
+
+    def add(filedata, meta, transaction, linkrev, p1, p2):
+        """Add a new revision to the store.
+
+        Takes file data, dictionary of metadata, a transaction, linkrev,
+        and parent nodes.
+
+        Returns the node that was added.
+
+        May no-op if a revision matching the supplied data is already stored.
+        """
+
+    def addrevision(revisiondata, transaction, linkrev, p1, p2, node=None,
+                    flags=0, cachedelta=None):
+        """Add a new revision to the store.
+
+        This is similar to ``add()`` except it operates at a lower level.
+
+        The data passed in already contains a metadata header, if any.
+
+        ``node`` and ``flags`` can be used to define the expected node and
+        the flags to use with storage. ``flags`` is a bitwise value composed
+        of the various ``REVISION_FLAG_*`` constants.
+
+        ``add()`` is usually called when adding files from e.g. the working
+        directory. ``addrevision()`` is often called by ``add()`` and for
+        scenarios where revision data has already been computed, such as when
+        applying raw data from a peer repo.
+        """
+
+    def addgroup(deltas, linkmapper, transaction, addrevisioncb=None,
+                 maybemissingparents=False):
+        """Process a series of deltas for storage.
+
+        ``deltas`` is an iterable of 7-tuples of
+        (node, p1, p2, linknode, deltabase, delta, flags) defining revisions
+        to add.
+
+        The ``delta`` field contains ``mpatch`` data to apply to a base
+        revision, identified by ``deltabase``. The base node can be
+        ``nullid``, in which case the header from the delta can be ignored
+        and the delta used as the fulltext.
+
+        ``addrevisioncb`` should be called for each node as it is committed.
+
+        ``maybemissingparents`` is a bool indicating whether the incoming
+        data may reference parents/ancestor revisions that aren't present.
+        This flag is set when receiving data into a "shallow" store that
+        doesn't hold all history.
+
+        Returns a list of nodes that were processed. A node will be in the list
+        even if it existed in the store previously.
+        """
+
+    def censorrevision(tr, node, tombstone=b''):
+        """Remove the content of a single revision.
+
+        The specified ``node`` will have its content purged from storage.
+        Future attempts to access the revision data for this node will
+        result in failure.
+
+        A ``tombstone`` message can optionally be stored. This message may be
+        displayed to users when they attempt to access the missing revision
+        data.
+
+        Storage backends may have stored deltas against the previous content
+        in this revision. As part of censoring a revision, these storage
+        backends are expected to rewrite any internally stored deltas such
+        that they no longer reference the deleted content.
+        """
+
+    def getstrippoint(minlink):
+        """Find the minimum revision that must be stripped to strip a linkrev.
+
+        Returns a 2-tuple containing the minimum revision number and a set
+        of all revisions numbers that would be broken by this strip.
+
+        TODO this is highly revlog centric and should be abstracted into
+        a higher-level deletion API. ``repair.strip()`` relies on this.
+        """
+
+    def strip(minlink, transaction):
+        """Remove storage of items starting at a linkrev.
+
+        This uses ``getstrippoint()`` to determine the first node to remove.
+        Then it effectively truncates storage for all revisions after that.
+
+        TODO this is highly revlog centric and should be abstracted into a
+        higher-level deletion API.
+        """
+
+class ifilestorage(ifileindex, ifiledata, ifilemutation):
+    """Complete storage interface for a single tracked file."""
+
+    def files():
+        """Obtain paths that are backing storage for this file.
+
+        TODO this is used heavily by verify code and there should probably
+        be a better API for that.
+        """
+
+    def storageinfo(exclusivefiles=False, sharedfiles=False,
+                    revisionscount=False, trackedsize=False,
+                    storedsize=False):
+        """Obtain information about storage for this file's data.
+
+        Returns a dict describing storage for this tracked path. The keys
+        in the dict map to arguments of the same. The arguments are bools
+        indicating whether to calculate and obtain that data.
+
+        exclusivefiles
+           Iterable of (vfs, path) describing files that are exclusively
+           used to back storage for this tracked path.
+
+        sharedfiles
+           Iterable of (vfs, path) describing files that are used to back
+           storage for this tracked path. Those files may also provide storage
+           for other stored entities.
+
+        revisionscount
+           Number of revisions available for retrieval.
+
+        trackedsize
+           Total size in bytes of all tracked revisions. This is a sum of the
+           length of the fulltext of all revisions.
+
+        storedsize
+           Total size in bytes used to store data for all tracked revisions.
+           This is commonly less than ``trackedsize`` due to internal usage
+           of deltas rather than fulltext revisions.
+
+        Not all storage backends may support all queries are have a reasonable
+        value to use. In that case, the value should be set to ``None`` and
+        callers are expected to handle this special value.
+        """
+
+    def verifyintegrity(state):
+        """Verifies the integrity of file storage.
+
+        ``state`` is a dict holding state of the verifier process. It can be
+        used to communicate data between invocations of multiple storage
+        primitives.
+
+        If individual revisions cannot have their revision content resolved,
+        the method is expected to set the ``skipread`` key to a set of nodes
+        that encountered problems.
+
+        The method yields objects conforming to the ``iverifyproblem``
+        interface.
+        """
+
+class idirs(interfaceutil.Interface):
+    """Interface representing a collection of directories from paths.
+
+    This interface is essentially a derived data structure representing
+    directories from a collection of paths.
+    """
+
+    def addpath(path):
+        """Add a path to the collection.
+
+        All directories in the path will be added to the collection.
+        """
+
+    def delpath(path):
+        """Remove a path from the collection.
+
+        If the removal was the last path in a particular directory, the
+        directory is removed from the collection.
+        """
+
+    def __iter__():
+        """Iterate over the directories in this collection of paths."""
+
+    def __contains__(path):
+        """Whether a specific directory is in this collection."""
+
+class imanifestdict(interfaceutil.Interface):
+    """Interface representing a manifest data structure.
+
+    A manifest is effectively a dict mapping paths to entries. Each entry
+    consists of a binary node and extra flags affecting that entry.
+    """
+
+    def __getitem__(path):
+        """Returns the binary node value for a path in the manifest.
+
+        Raises ``KeyError`` if the path does not exist in the manifest.
+
+        Equivalent to ``self.find(path)[0]``.
+        """
+
+    def find(path):
+        """Returns the entry for a path in the manifest.
+
+        Returns a 2-tuple of (node, flags).
+
+        Raises ``KeyError`` if the path does not exist in the manifest.
+        """
+
+    def __len__():
+        """Return the number of entries in the manifest."""
+
+    def __nonzero__():
+        """Returns True if the manifest has entries, False otherwise."""
+
+    __bool__ = __nonzero__
+
+    def __setitem__(path, node):
+        """Define the node value for a path in the manifest.
+
+        If the path is already in the manifest, its flags will be copied to
+        the new entry.
+        """
+
+    def __contains__(path):
+        """Whether a path exists in the manifest."""
+
+    def __delitem__(path):
+        """Remove a path from the manifest.
+
+        Raises ``KeyError`` if the path is not in the manifest.
+        """
+
+    def __iter__():
+        """Iterate over paths in the manifest."""
+
+    def iterkeys():
+        """Iterate over paths in the manifest."""
+
+    def keys():
+        """Obtain a list of paths in the manifest."""
+
+    def filesnotin(other, match=None):
+        """Obtain the set of paths in this manifest but not in another.
+
+        ``match`` is an optional matcher function to be applied to both
+        manifests.
+
+        Returns a set of paths.
+        """
+
+    def dirs():
+        """Returns an object implementing the ``idirs`` interface."""
+
+    def hasdir(dir):
+        """Returns a bool indicating if a directory is in this manifest."""
+
+    def matches(match):
+        """Generate a new manifest filtered through a matcher.
+
+        Returns an object conforming to the ``imanifestdict`` interface.
+        """
+
+    def walk(match):
+        """Generator of paths in manifest satisfying a matcher.
+
+        This is equivalent to ``self.matches(match).iterkeys()`` except a new
+        manifest object is not created.
+
+        If the matcher has explicit files listed and they don't exist in
+        the manifest, ``match.bad()`` is called for each missing file.
+        """
+
+    def diff(other, match=None, clean=False):
+        """Find differences between this manifest and another.
+
+        This manifest is compared to ``other``.
+
+        If ``match`` is provided, the two manifests are filtered against this
+        matcher and only entries satisfying the matcher are compared.
+
+        If ``clean`` is True, unchanged files are included in the returned
+        object.
+
+        Returns a dict with paths as keys and values of 2-tuples of 2-tuples of
+        the form ``((node1, flag1), (node2, flag2))`` where ``(node1, flag1)``
+        represents the node and flags for this manifest and ``(node2, flag2)``
+        are the same for the other manifest.
+        """
+
+    def setflag(path, flag):
+        """Set the flag value for a given path.
+
+        Raises ``KeyError`` if the path is not already in the manifest.
+        """
+
+    def get(path, default=None):
+        """Obtain the node value for a path or a default value if missing."""
+
+    def flags(path, default=''):
+        """Return the flags value for a path or a default value if missing."""
+
+    def copy():
+        """Return a copy of this manifest."""
+
+    def items():
+        """Returns an iterable of (path, node) for items in this manifest."""
+
+    def iteritems():
+        """Identical to items()."""
+
+    def iterentries():
+        """Returns an iterable of (path, node, flags) for this manifest.
+
+        Similar to ``iteritems()`` except items are a 3-tuple and include
+        flags.
+        """
+
+    def text():
+        """Obtain the raw data representation for this manifest.
+
+        Result is used to create a manifest revision.
+        """
+
+    def fastdelta(base, changes):
+        """Obtain a delta between this manifest and another given changes.
+
+        ``base`` in the raw data representation for another manifest.
+
+        ``changes`` is an iterable of ``(path, to_delete)``.
+
+        Returns a 2-tuple containing ``bytearray(self.text())`` and the
+        delta between ``base`` and this manifest.
+        """
+
+class imanifestrevisionbase(interfaceutil.Interface):
+    """Base interface representing a single revision of a manifest.
+
+    Should not be used as a primary interface: should always be inherited
+    as part of a larger interface.
+    """
+
+    def new():
+        """Obtain a new manifest instance.
+
+        Returns an object conforming to the ``imanifestrevisionwritable``
+        interface. The instance will be associated with the same
+        ``imanifestlog`` collection as this instance.
+        """
+
+    def copy():
+        """Obtain a copy of this manifest instance.
+
+        Returns an object conforming to the ``imanifestrevisionwritable``
+        interface. The instance will be associated with the same
+        ``imanifestlog`` collection as this instance.
+        """
+
+    def read():
+        """Obtain the parsed manifest data structure.
+
+        The returned object conforms to the ``imanifestdict`` interface.
+        """
+
+class imanifestrevisionstored(imanifestrevisionbase):
+    """Interface representing a manifest revision committed to storage."""
+
+    def node():
+        """The binary node for this manifest."""
+
+    parents = interfaceutil.Attribute(
+        """List of binary nodes that are parents for this manifest revision."""
+    )
+
+    def readdelta(shallow=False):
+        """Obtain the manifest data structure representing changes from parent.
+
+        This manifest is compared to its 1st parent. A new manifest representing
+        those differences is constructed.
+
+        The returned object conforms to the ``imanifestdict`` interface.
+        """
+
+    def readfast(shallow=False):
+        """Calls either ``read()`` or ``readdelta()``.
+
+        The faster of the two options is called.
+        """
+
+    def find(key):
+        """Calls self.read().find(key)``.
+
+        Returns a 2-tuple of ``(node, flags)`` or raises ``KeyError``.
+        """
+
+class imanifestrevisionwritable(imanifestrevisionbase):
+    """Interface representing a manifest revision that can be committed."""
+
+    def write(transaction, linkrev, p1node, p2node, added, removed, match=None):
+        """Add this revision to storage.
+
+        Takes a transaction object, the changeset revision number it will
+        be associated with, its parent nodes, and lists of added and
+        removed paths.
+
+        If match is provided, storage can choose not to inspect or write out
+        items that do not match. Storage is still required to be able to provide
+        the full manifest in the future for any directories written (these
+        manifests should not be "narrowed on disk").
+
+        Returns the binary node of the created revision.
+        """
+
+class imanifeststorage(interfaceutil.Interface):
+    """Storage interface for manifest data."""
+
+    tree = interfaceutil.Attribute(
+        """The path to the directory this manifest tracks.
+
+        The empty bytestring represents the root manifest.
+        """)
+
+    index = interfaceutil.Attribute(
+        """An ``ifilerevisionssequence`` instance.""")
+
+    indexfile = interfaceutil.Attribute(
+        """Path of revlog index file.
+
+        TODO this is revlog specific and should not be exposed.
+        """)
+
+    opener = interfaceutil.Attribute(
+        """VFS opener to use to access underlying files used for storage.
+
+        TODO this is revlog specific and should not be exposed.
+        """)
+
+    version = interfaceutil.Attribute(
+        """Revlog version number.
+
+        TODO this is revlog specific and should not be exposed.
+        """)
+
+    _generaldelta = interfaceutil.Attribute(
+        """Whether generaldelta storage is being used.
+
+        TODO this is revlog specific and should not be exposed.
+        """)
+
+    fulltextcache = interfaceutil.Attribute(
+        """Dict with cache of fulltexts.
+
+        TODO this doesn't feel appropriate for the storage interface.
+        """)
+
+    def __len__():
+        """Obtain the number of revisions stored for this manifest."""
+
+    def __iter__():
+        """Iterate over revision numbers for this manifest."""
+
+    def rev(node):
+        """Obtain the revision number given a binary node.
+
+        Raises ``error.LookupError`` if the node is not known.
+        """
+
+    def node(rev):
+        """Obtain the node value given a revision number.
+
+        Raises ``error.LookupError`` if the revision is not known.
+        """
+
+    def lookup(value):
+        """Attempt to resolve a value to a node.
+
+        Value can be a binary node, hex node, revision number, or a bytes
+        that can be converted to an integer.
+
+        Raises ``error.LookupError`` if a ndoe could not be resolved.
+        """
+
+    def parents(node):
+        """Returns a 2-tuple of parent nodes for a node.
+
+        Values will be ``nullid`` if the parent is empty.
+        """
+
+    def parentrevs(rev):
+        """Like parents() but operates on revision numbers."""
+
+    def linkrev(rev):
+        """Obtain the changeset revision number a revision is linked to."""
+
+    def revision(node, _df=None, raw=False):
+        """Obtain fulltext data for a node."""
+
+    def rawdata(node, _df=None):
+        """Obtain raw data for a node."""
+
+    def revdiff(rev1, rev2):
+        """Obtain a delta between two revision numbers.
+
+        The returned data is the result of ``bdiff.bdiff()`` on the raw
+        revision data.
+        """
+
+    def cmp(node, fulltext):
+        """Compare fulltext to another revision.
+
+        Returns True if the fulltext is different from what is stored.
+        """
+
+    def emitrevisions(nodes,
+                      nodesorder=None,
+                      revisiondata=False,
+                      assumehaveparentrevisions=False):
+        """Produce ``irevisiondelta`` describing revisions.
+
+        See the documentation for ``ifiledata`` for more.
+        """
+
+    def addgroup(deltas, linkmapper, transaction, addrevisioncb=None):
+        """Process a series of deltas for storage.
+
+        See the documentation in ``ifilemutation`` for more.
+        """
+
+    def rawsize(rev):
+        """Obtain the size of tracked data.
+
+        Is equivalent to ``len(m.rawdata(node))``.
+
+        TODO this method is only used by upgrade code and may be removed.
+        """
+
+    def getstrippoint(minlink):
+        """Find minimum revision that must be stripped to strip a linkrev.
+
+        See the documentation in ``ifilemutation`` for more.
+        """
+
+    def strip(minlink, transaction):
+        """Remove storage of items starting at a linkrev.
+
+        See the documentation in ``ifilemutation`` for more.
+        """
+
+    def checksize():
+        """Obtain the expected sizes of backing files.
+
+        TODO this is used by verify and it should not be part of the interface.
+        """
+
+    def files():
+        """Obtain paths that are backing storage for this manifest.
+
+        TODO this is used by verify and there should probably be a better API
+        for this functionality.
+        """
+
+    def deltaparent(rev):
+        """Obtain the revision that a revision is delta'd against.
+
+        TODO delta encoding is an implementation detail of storage and should
+        not be exposed to the storage interface.
+        """
+
+    def clone(tr, dest, **kwargs):
+        """Clone this instance to another."""
+
+    def clearcaches(clear_persisted_data=False):
+        """Clear any caches associated with this instance."""
+
+    def dirlog(d):
+        """Obtain a manifest storage instance for a tree."""
+
+    def add(m, transaction, link, p1, p2, added, removed, readtree=None,
+            match=None):
+        """Add a revision to storage.
+
+        ``m`` is an object conforming to ``imanifestdict``.
+
+        ``link`` is the linkrev revision number.
+
+        ``p1`` and ``p2`` are the parent revision numbers.
+
+        ``added`` and ``removed`` are iterables of added and removed paths,
+        respectively.
+
+        ``readtree`` is a function that can be used to read the child tree(s)
+        when recursively writing the full tree structure when using
+        treemanifets.
+
+        ``match`` is a matcher that can be used to hint to storage that not all
+        paths must be inspected; this is an optimization and can be safely
+        ignored. Note that the storage must still be able to reproduce a full
+        manifest including files that did not match.
+        """
+
+    def storageinfo(exclusivefiles=False, sharedfiles=False,
+                    revisionscount=False, trackedsize=False,
+                    storedsize=False):
+        """Obtain information about storage for this manifest's data.
+
+        See ``ifilestorage.storageinfo()`` for a description of this method.
+        This one behaves the same way, except for manifest data.
+        """
+
+class imanifestlog(interfaceutil.Interface):
+    """Interface representing a collection of manifest snapshots.
+
+    Represents the root manifest in a repository.
+
+    Also serves as a means to access nested tree manifests and to cache
+    tree manifests.
+    """
+
+    def __getitem__(node):
+        """Obtain a manifest instance for a given binary node.
+
+        Equivalent to calling ``self.get('', node)``.
+
+        The returned object conforms to the ``imanifestrevisionstored``
+        interface.
+        """
+
+    def get(tree, node, verify=True):
+        """Retrieve the manifest instance for a given directory and binary node.
+
+        ``node`` always refers to the node of the root manifest (which will be
+        the only manifest if flat manifests are being used).
+
+        If ``tree`` is the empty string, the root manifest is returned.
+        Otherwise the manifest for the specified directory will be returned
+        (requires tree manifests).
+
+        If ``verify`` is True, ``LookupError`` is raised if the node is not
+        known.
+
+        The returned object conforms to the ``imanifestrevisionstored``
+        interface.
+        """
+
+    def getstorage(tree):
+        """Retrieve an interface to storage for a particular tree.
+
+        If ``tree`` is the empty bytestring, storage for the root manifest will
+        be returned. Otherwise storage for a tree manifest is returned.
+
+        TODO formalize interface for returned object.
+        """
+
+    def clearcaches():
+        """Clear caches associated with this collection."""
+
+    def rev(node):
+        """Obtain the revision number for a binary node.
+
+        Raises ``error.LookupError`` if the node is not known.
+        """
+
+class ilocalrepositoryfilestorage(interfaceutil.Interface):
+    """Local repository sub-interface providing access to tracked file storage.
+
+    This interface defines how a repository accesses storage for a single
+    tracked file path.
+    """
+
+    def file(f):
+        """Obtain a filelog for a tracked path.
+
+        The returned type conforms to the ``ifilestorage`` interface.
+        """
+
+class ilocalrepositorymain(interfaceutil.Interface):
+    """Main interface for local repositories.
+
+    This currently captures the reality of things - not how things should be.
+    """
+
+    supportedformats = interfaceutil.Attribute(
+        """Set of requirements that apply to stream clone.
+
+        This is actually a class attribute and is shared among all instances.
+        """)
+
+    supported = interfaceutil.Attribute(
+        """Set of requirements that this repo is capable of opening.""")
+
+    requirements = interfaceutil.Attribute(
+        """Set of requirements this repo uses.""")
+
+    features = interfaceutil.Attribute(
+        """Set of "features" this repository supports.
+
+        A "feature" is a loosely-defined term. It can refer to a feature
+        in the classical sense or can describe an implementation detail
+        of the repository. For example, a ``readonly`` feature may denote
+        the repository as read-only. Or a ``revlogfilestore`` feature may
+        denote that the repository is using revlogs for file storage.
+
+        The intent of features is to provide a machine-queryable mechanism
+        for repo consumers to test for various repository characteristics.
+
+        Features are similar to ``requirements``. The main difference is that
+        requirements are stored on-disk and represent requirements to open the
+        repository. Features are more run-time capabilities of the repository
+        and more granular capabilities (which may be derived from requirements).
+        """)
+
+    filtername = interfaceutil.Attribute(
+        """Name of the repoview that is active on this repo.""")
+
+    wvfs = interfaceutil.Attribute(
+        """VFS used to access the working directory.""")
+
+    vfs = interfaceutil.Attribute(
+        """VFS rooted at the .hg directory.
+
+        Used to access repository data not in the store.
+        """)
+
+    svfs = interfaceutil.Attribute(
+        """VFS rooted at the store.
+
+        Used to access repository data in the store. Typically .hg/store.
+        But can point elsewhere if the store is shared.
+        """)
+
+    root = interfaceutil.Attribute(
+        """Path to the root of the working directory.""")
+
+    path = interfaceutil.Attribute(
+        """Path to the .hg directory.""")
+
+    origroot = interfaceutil.Attribute(
+        """The filesystem path that was used to construct the repo.""")
+
+    auditor = interfaceutil.Attribute(
+        """A pathauditor for the working directory.
+
+        This checks if a path refers to a nested repository.
+
+        Operates on the filesystem.
+        """)
+
+    nofsauditor = interfaceutil.Attribute(
+        """A pathauditor for the working directory.
+
+        This is like ``auditor`` except it doesn't do filesystem checks.
+        """)
+
+    baseui = interfaceutil.Attribute(
+        """Original ui instance passed into constructor.""")
+
+    ui = interfaceutil.Attribute(
+        """Main ui instance for this instance.""")
+
+    sharedpath = interfaceutil.Attribute(
+        """Path to the .hg directory of the repo this repo was shared from.""")
+
+    store = interfaceutil.Attribute(
+        """A store instance.""")
+
+    spath = interfaceutil.Attribute(
+        """Path to the store.""")
+
+    sjoin = interfaceutil.Attribute(
+        """Alias to self.store.join.""")
+
+    cachevfs = interfaceutil.Attribute(
+        """A VFS used to access the cache directory.
+
+        Typically .hg/cache.
+        """)
+
+    wcachevfs = interfaceutil.Attribute(
+        """A VFS used to access the cache directory dedicated to working copy
+
+        Typically .hg/wcache.
+        """)
+
+    filteredrevcache = interfaceutil.Attribute(
+        """Holds sets of revisions to be filtered.""")
+
+    names = interfaceutil.Attribute(
+        """A ``namespaces`` instance.""")
+
+    def close():
+        """Close the handle on this repository."""
+
+    def peer():
+        """Obtain an object conforming to the ``peer`` interface."""
+
+    def unfiltered():
+        """Obtain an unfiltered/raw view of this repo."""
+
+    def filtered(name, visibilityexceptions=None):
+        """Obtain a named view of this repository."""
+
+    obsstore = interfaceutil.Attribute(
+        """A store of obsolescence data.""")
+
+    changelog = interfaceutil.Attribute(
+        """A handle on the changelog revlog.""")
+
+    manifestlog = interfaceutil.Attribute(
+        """An instance conforming to the ``imanifestlog`` interface.
+
+        Provides access to manifests for the repository.
+        """)
+
+    dirstate = interfaceutil.Attribute(
+        """Working directory state.""")
+
+    narrowpats = interfaceutil.Attribute(
+        """Matcher patterns for this repository's narrowspec.""")
+
+    def narrowmatch(match=None, includeexact=False):
+        """Obtain a matcher for the narrowspec."""
+
+    def setnarrowpats(newincludes, newexcludes):
+        """Define the narrowspec for this repository."""
+
+    def __getitem__(changeid):
+        """Try to resolve a changectx."""
+
+    def __contains__(changeid):
+        """Whether a changeset exists."""
+
+    def __nonzero__():
+        """Always returns True."""
+        return True
+
+    __bool__ = __nonzero__
+
+    def __len__():
+        """Returns the number of changesets in the repo."""
+
+    def __iter__():
+        """Iterate over revisions in the changelog."""
+
+    def revs(expr, *args):
+        """Evaluate a revset.
+
+        Emits revisions.
+        """
+
+    def set(expr, *args):
+        """Evaluate a revset.
+
+        Emits changectx instances.
+        """
+
+    def anyrevs(specs, user=False, localalias=None):
+        """Find revisions matching one of the given revsets."""
+
+    def url():
+        """Returns a string representing the location of this repo."""
+
+    def hook(name, throw=False, **args):
+        """Call a hook."""
+
+    def tags():
+        """Return a mapping of tag to node."""
+
+    def tagtype(tagname):
+        """Return the type of a given tag."""
+
+    def tagslist():
+        """Return a list of tags ordered by revision."""
+
+    def nodetags(node):
+        """Return the tags associated with a node."""
+
+    def nodebookmarks(node):
+        """Return the list of bookmarks pointing to the specified node."""
+
+    def branchmap():
+        """Return a mapping of branch to heads in that branch."""
+
+    def revbranchcache():
+        pass
+
+    def branchtip(branchtip, ignoremissing=False):
+        """Return the tip node for a given branch."""
+
+    def lookup(key):
+        """Resolve the node for a revision."""
+
+    def lookupbranch(key):
+        """Look up the branch name of the given revision or branch name."""
+
+    def known(nodes):
+        """Determine whether a series of nodes is known.
+
+        Returns a list of bools.
+        """
+
+    def local():
+        """Whether the repository is local."""
+        return True
+
+    def publishing():
+        """Whether the repository is a publishing repository."""
+
+    def cancopy():
+        pass
+
+    def shared():
+        """The type of shared repository or None."""
+
+    def wjoin(f, *insidef):
+        """Calls self.vfs.reljoin(self.root, f, *insidef)"""
+
+    def setparents(p1, p2):
+        """Set the parent nodes of the working directory."""
+
+    def filectx(path, changeid=None, fileid=None):
+        """Obtain a filectx for the given file revision."""
+
+    def getcwd():
+        """Obtain the current working directory from the dirstate."""
+
+    def pathto(f, cwd=None):
+        """Obtain the relative path to a file."""
+
+    def adddatafilter(name, fltr):
+        pass
+
+    def wread(filename):
+        """Read a file from wvfs, using data filters."""
+
+    def wwrite(filename, data, flags, backgroundclose=False, **kwargs):
+        """Write data to a file in the wvfs, using data filters."""
+
+    def wwritedata(filename, data):
+        """Resolve data for writing to the wvfs, using data filters."""
+
+    def currenttransaction():
+        """Obtain the current transaction instance or None."""
+
+    def transaction(desc, report=None):
+        """Open a new transaction to write to the repository."""
+
+    def undofiles():
+        """Returns a list of (vfs, path) for files to undo transactions."""
+
+    def recover():
+        """Roll back an interrupted transaction."""
+
+    def rollback(dryrun=False, force=False):
+        """Undo the last transaction.
+
+        DANGEROUS.
+        """
+
+    def updatecaches(tr=None, full=False):
+        """Warm repo caches."""
+
+    def invalidatecaches():
+        """Invalidate cached data due to the repository mutating."""
+
+    def invalidatevolatilesets():
+        pass
+
+    def invalidatedirstate():
+        """Invalidate the dirstate."""
+
+    def invalidate(clearfilecache=False):
+        pass
+
+    def invalidateall():
+        pass
+
+    def lock(wait=True):
+        """Lock the repository store and return a lock instance."""
+
+    def wlock(wait=True):
+        """Lock the non-store parts of the repository."""
+
+    def currentwlock():
+        """Return the wlock if it's held or None."""
+
+    def checkcommitpatterns(wctx, vdirs, match, status, fail):
+        pass
+
+    def commit(text='', user=None, date=None, match=None, force=False,
+               editor=False, extra=None):
+        """Add a new revision to the repository."""
+
+    def commitctx(ctx, error=False, origctx=None):
+        """Commit a commitctx instance to the repository."""
+
+    def destroying():
+        """Inform the repository that nodes are about to be destroyed."""
+
+    def destroyed():
+        """Inform the repository that nodes have been destroyed."""
+
+    def status(node1='.', node2=None, match=None, ignored=False,
+               clean=False, unknown=False, listsubrepos=False):
+        """Convenience method to call repo[x].status()."""
+
+    def addpostdsstatus(ps):
+        pass
+
+    def postdsstatus():
+        pass
+
+    def clearpostdsstatus():
+        pass
+
+    def heads(start=None):
+        """Obtain list of nodes that are DAG heads."""
+
+    def branchheads(branch=None, start=None, closed=False):
+        pass
+
+    def branches(nodes):
+        pass
+
+    def between(pairs):
+        pass
+
+    def checkpush(pushop):
+        pass
+
+    prepushoutgoinghooks = interfaceutil.Attribute(
+        """util.hooks instance.""")
+
+    def pushkey(namespace, key, old, new):
+        pass
+
+    def listkeys(namespace):
+        pass
+
+    def debugwireargs(one, two, three=None, four=None, five=None):
+        pass
+
+    def savecommitmessage(text):
+        pass
+
+class completelocalrepository(ilocalrepositorymain,
+                              ilocalrepositoryfilestorage):
+    """Complete interface for a local repository."""
+
+class iwireprotocolcommandcacher(interfaceutil.Interface):
+    """Represents a caching backend for wire protocol commands.
+
+    Wire protocol version 2 supports transparent caching of many commands.
+    To leverage this caching, servers can activate objects that cache
+    command responses. Objects handle both cache writing and reading.
+    This interface defines how that response caching mechanism works.
+
+    Wire protocol version 2 commands emit a series of objects that are
+    serialized and sent to the client. The caching layer exists between
+    the invocation of the command function and the sending of its output
+    objects to an output layer.
+
+    Instances of this interface represent a binding to a cache that
+    can serve a response (in place of calling a command function) and/or
+    write responses to a cache for subsequent use.
+
+    When a command request arrives, the following happens with regards
+    to this interface:
+
+    1. The server determines whether the command request is cacheable.
+    2. If it is, an instance of this interface is spawned.
+    3. The cacher is activated in a context manager (``__enter__`` is called).
+    4. A cache *key* for that request is derived. This will call the
+       instance's ``adjustcachekeystate()`` method so the derivation
+       can be influenced.
+    5. The cacher is informed of the derived cache key via a call to
+       ``setcachekey()``.
+    6. The cacher's ``lookup()`` method is called to test for presence of
+       the derived key in the cache.
+    7. If ``lookup()`` returns a hit, that cached result is used in place
+       of invoking the command function. ``__exit__`` is called and the instance
+       is discarded.
+    8. The command function is invoked.
+    9. ``onobject()`` is called for each object emitted by the command
+       function.
+    10. After the final object is seen, ``onfinished()`` is called.
+    11. ``__exit__`` is called to signal the end of use of the instance.
+
+    Cache *key* derivation can be influenced by the instance.
+
+    Cache keys are initially derived by a deterministic representation of
+    the command request. This includes the command name, arguments, protocol
+    version, etc. This initial key derivation is performed by CBOR-encoding a
+    data structure and feeding that output into a hasher.
+
+    Instances of this interface can influence this initial key derivation
+    via ``adjustcachekeystate()``.
+
+    The instance is informed of the derived cache key via a call to
+    ``setcachekey()``. The instance must store the key locally so it can
+    be consulted on subsequent operations that may require it.
+
+    When constructed, the instance has access to a callable that can be used
+    for encoding response objects. This callable receives as its single
+    argument an object emitted by a command function. It returns an iterable
+    of bytes chunks representing the encoded object. Unless the cacher is
+    caching native Python objects in memory or has a way of reconstructing
+    the original Python objects, implementations typically call this function
+    to produce bytes from the output objects and then store those bytes in
+    the cache. When it comes time to re-emit those bytes, they are wrapped
+    in a ``wireprototypes.encodedresponse`` instance to tell the output
+    layer that they are pre-encoded.
+
+    When receiving the objects emitted by the command function, instances
+    can choose what to do with those objects. The simplest thing to do is
+    re-emit the original objects. They will be forwarded to the output
+    layer and will be processed as if the cacher did not exist.
+
+    Implementations could also choose to not emit objects - instead locally
+    buffering objects or their encoded representation. They could then emit
+    a single "coalesced" object when ``onfinished()`` is called. In
+    this way, the implementation would function as a filtering layer of
+    sorts.
+
+    When caching objects, typically the encoded form of the object will
+    be stored. Keep in mind that if the original object is forwarded to
+    the output layer, it will need to be encoded there as well. For large
+    output, this redundant encoding could add overhead. Implementations
+    could wrap the encoded object data in ``wireprototypes.encodedresponse``
+    instances to avoid this overhead.
+    """
+    def __enter__():
+        """Marks the instance as active.
+
+        Should return self.
+        """
+
+    def __exit__(exctype, excvalue, exctb):
+        """Called when cacher is no longer used.
+
+        This can be used by implementations to perform cleanup actions (e.g.
+        disconnecting network sockets, aborting a partially cached response.
+        """
+
+    def adjustcachekeystate(state):
+        """Influences cache key derivation by adjusting state to derive key.
+
+        A dict defining the state used to derive the cache key is passed.
+
+        Implementations can modify this dict to record additional state that
+        is wanted to influence key derivation.
+
+        Implementations are *highly* encouraged to not modify or delete
+        existing keys.
+        """
+
+    def setcachekey(key):
+        """Record the derived cache key for this request.
+
+        Instances may mutate the key for internal usage, as desired. e.g.
+        instances may wish to prepend the repo name, introduce path
+        components for filesystem or URL addressing, etc. Behavior is up to
+        the cache.
+
+        Returns a bool indicating if the request is cacheable by this
+        instance.
+        """
+
+    def lookup():
+        """Attempt to resolve an entry in the cache.
+
+        The instance is instructed to look for the cache key that it was
+        informed about via the call to ``setcachekey()``.
+
+        If there's no cache hit or the cacher doesn't wish to use the cached
+        entry, ``None`` should be returned.
+
+        Else, a dict defining the cached result should be returned. The
+        dict may have the following keys:
+
+        objs
+           An iterable of objects that should be sent to the client. That
+           iterable of objects is expected to be what the command function
+           would return if invoked or an equivalent representation thereof.
+        """
+
+    def onobject(obj):
+        """Called when a new object is emitted from the command function.
+
+        Receives as its argument the object that was emitted from the
+        command function.
+
+        This method returns an iterator of objects to forward to the output
+        layer. The easiest implementation is a generator that just
+        ``yield obj``.
+        """
+
+    def onfinished():
+        """Called after all objects have been emitted from the command function.
+
+        Implementations should return an iterator of objects to forward to
+        the output layer.
+
+        This method can be a generator.
+        """