diff -r def497c75351 -r bc88aa7472de hgext/chainsaw.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hgext/chainsaw.py	Sat Nov 26 12:23:56 2022 +0100
@@ -0,0 +1,156 @@
+# chainsaw.py
+#
+# Copyright 2022 Georges Racinet <georges.racinet@octobus.net>
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+"""chainsaw is a collection of single-minded and dangerous tools. (EXPERIMENTAL)
+
+  "Don't use a chainsaw to cut your food!"
+
+The chainsaw extension provides commands that are so much geared towards a
+specific use case in a specific context or environment that they are totally
+inappropriate and **really dangerous** in other contexts.
+
+The help text of each command explicitly summarizes its context of application
+and the wanted end result.
+
+It is recommended to run these commands with the ``HGPLAIN`` environment
+variable (see :hg:`help scripting`).
+"""
+
+import shutil
+
+from mercurial.i18n import _
+from mercurial import (
+    cmdutil,
+    commands,
+    error,
+    registrar,
+)
+
+cmdtable = {}
+command = registrar.command(cmdtable)
+# Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
+# extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
+# be specifying the version(s) of Mercurial they are tested with, or
+# leave the attribute unspecified.
+testedwith = b'ships-with-hg-core'
+
+
+@command(
+    b'admin::chainsaw-update',
+    [
+        (
+            b'',
+            b'purge-unknown',
+            True,
+            _(
+                b'Remove unversioned files before update. Disabling this can '
+                b'in some cases interfere with the update.'
+                b'See also :hg:`purge`.'
+            ),
+        ),
+        (
+            b'',
+            b'purge-ignored',
+            True,
+            _(
+                b'Remove ignored files before update. Disable this for '
+                b'instance to reuse previous compiler object files. '
+                b'See also :hg:`purge`.'
+            ),
+        ),
+        (
+            b'',
+            b'rev',
+            b'',
+            _(b'revision to update to'),
+        ),
+        (
+            b'',
+            b'source',
+            b'',
+            _(b'repository to clone from'),
+        ),
+    ],
+    _(b'hg admin::chainsaw-update [OPTION] --rev REV --source SOURCE...'),
+    helpbasic=True,
+)
+def update(ui, repo, **opts):
+    """pull and update to a given revision, no matter what, (EXPERIMENTAL)
+
+    Context of application: *some* Continuous Integration (CI) systems,
+    packaging or deployment tools.
+
+    Wanted end result: clean working directory updated at the given revision.
+
+    chainsaw-update pulls from one source, then updates the working directory
+    to the given revision, overcoming anything that would stand in the way.
+
+    By default, it will:
+
+    - break locks if needed, leading to possible corruption if there
+      is a concurrent write access.
+    - perform recovery actions if needed
+    - revert any local modification.
+    - purge unknown and ignored files.
+    - go as far as to reclone if everything else failed (not implemented yet).
+
+    DO NOT use it for anything else than performing a series
+    of unattended updates, with full exclusive repository access each time
+    and without any other local work than running build scripts.
+    In case the local repository is a share (see :hg:`help share`), exclusive
+    write access to the share source is also mandatory.
+
+    It is recommended to run these commands with the ``HGPLAIN`` environment
+    variable (see :hg:`scripting`).
+
+    Motivation: in Continuous Integration and Delivery systems (CI/CD), the
+    occasional remnant or bogus lock are common sources of waste of time (both
+    working time and calendar time). CI/CD scripts tend to grow with counter-
+    measures, often done in urgency. Also, whilst it is neat to keep
+    repositories from one job to the next (especially with large
+    repositories), an exceptional recloning is better than missing a release
+    deadline.
+    """
+    rev = opts['rev']
+    source = opts['source']
+    if not rev:
+        raise error.InputError(_(b'specify a target revision with --rev'))
+    if not source:
+        raise error.InputError(_(b'specify a pull path with --source'))
+    ui.status(_(b'breaking locks, if any\n'))
+    repo.svfs.tryunlink(b'lock')
+    repo.vfs.tryunlink(b'wlock')
+
+    ui.status(_(b'recovering after interrupted transaction, if any\n'))
+    repo.recover()
+
+    ui.status(_(b'pulling from %s\n') % source)
+    overrides = {(b'ui', b'quiet'): True}
+    with ui.configoverride(overrides, b'chainsaw-update'):
+        pull = cmdutil.findcmd(b'pull', commands.table)[1][0]
+        pull(ui, repo, source, rev=[rev], remote_hidden=False)
+
+    purge = cmdutil.findcmd(b'purge', commands.table)[1][0]
+    purge(
+        ui,
+        repo,
+        dirs=True,
+        all=opts.get('purge_ignored'),
+        files=opts.get('purge_unknown'),
+        confirm=False,
+    )
+
+    ui.status(_(b'updating to revision \'%s\'\n') % rev)
+    update = cmdutil.findcmd(b'update', commands.table)[1][0]
+    update(ui, repo, rev=rev, clean=True)
+
+    ui.status(
+        _(
+            b'chainsaw-update to revision \'%s\' '
+            b'for repository at \'%s\' done\n'
+        )
+        % (rev, repo.root)
+    )