--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mercurial/logexchange.py	Thu Dec 07 00:26:45 2017 +0530
@@ -0,0 +1,118 @@
+# logexchange.py
+#
+# Copyright 2017 Augie Fackler <raf@durin42.com>
+# Copyright 2017 Sean Farley <sean@farley.io>
+#
+# 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 .node import hex
+
+from . import (
+    vfs as vfsmod,
+)
+
+# directory name in .hg/ in which remotenames files will be present
+remotenamedir = 'logexchange'
+
+def readremotenamefile(repo, filename):
+    """
+    reads a file from .hg/logexchange/ directory and yields it's content
+    filename: the file to be read
+    yield a tuple (node, remotepath, name)
+    """
+
+    vfs = vfsmod.vfs(repo.vfs.join(remotenamedir))
+    if not vfs.exists(filename):
+        return
+    f = vfs(filename)
+    lineno = 0
+    for line in f:
+        line = line.strip()
+        if not line:
+            continue
+        # contains the version number
+        if lineno == 0:
+            lineno += 1
+        try:
+            node, remote, rname = line.split('\0')
+            yield node, remote, rname
+        except ValueError:
+            pass
+
+    f.close()
+
+def readremotenames(repo):
+    """
+    read the details about the remotenames stored in .hg/logexchange/ and
+    yields a tuple (node, remotepath, name). It does not yields information
+    about whether an entry yielded is branch or bookmark. To get that
+    information, call the respective functions.
+    """
+
+    for bmentry in readremotenamefile(repo, 'bookmarks'):
+        yield bmentry
+    for branchentry in readremotenamefile(repo, 'branches'):
+        yield branchentry
+
+def writeremotenamefile(repo, remotepath, names, nametype):
+    vfs = vfsmod.vfs(repo.vfs.join(remotenamedir))
+    f = vfs(nametype, 'w', atomictemp=True)
+    # write the storage version info on top of file
+    # version '0' represents the very initial version of the storage format
+    f.write('0\n\n')
+
+    olddata = set(readremotenamefile(repo, nametype))
+    # re-save the data from a different remote than this one.
+    for node, oldpath, rname in sorted(olddata):
+        if oldpath != remotepath:
+            f.write('%s\0%s\0%s\n' % (node, oldpath, rname))
+
+    for name, node in sorted(names.iteritems()):
+        if nametype == "branches":
+            for n in node:
+                f.write('%s\0%s\0%s\n' % (n, remotepath, name))
+        elif nametype == "bookmarks":
+            if node:
+                f.write('%s\0%s\0%s\n' % (node, remotepath, name))
+
+    f.close()
+
+def saveremotenames(repo, remotepath, branches=None, bookmarks=None):
+    """
+    save remotenames i.e. remotebookmarks and remotebranches in their
+    respective files under ".hg/logexchange/" directory.
+    """
+    wlock = repo.wlock()
+    try:
+        if bookmarks:
+            writeremotenamefile(repo, remotepath, bookmarks, 'bookmarks')
+        if branches:
+            writeremotenamefile(repo, remotepath, branches, 'branches')
+    finally:
+        wlock.release()
+
+def pullremotenames(localrepo, remoterepo):
+    """
+    pulls bookmarks and branches information of the remote repo during a
+    pull or clone operation.
+    localrepo is our local repository
+    remoterepo is the peer instance
+    """
+    remotepath = remoterepo.url()
+    bookmarks = remoterepo.listkeys('bookmarks')
+    # on a push, we don't want to keep obsolete heads since
+    # they won't show up as heads on the next pull, so we
+    # remove them here otherwise we would require the user
+    # to issue a pull to refresh the storage
+    bmap = {}
+    repo = localrepo.unfiltered()
+    for branch, nodes in remoterepo.branchmap().iteritems():
+        bmap[branch] = []
+        for node in nodes:
+            if node in repo and not repo[node].obsolete():
+                bmap[branch].append(hex(node))
+
+    saveremotenames(localrepo, remotepath, bmap, bookmarks)