Mercurial > hg
view hgext/share.py @ 32697:19b9fc40cc51
revlog: skeleton support for version 2 revlogs
There are a number of improvements we want to make to revlogs
that will require a new version - version 2. It is unclear what the
full set of improvements will be or when we'll be done with them.
What I do know is that the process will likely take longer than a
single release, will require input from various stakeholders to
evaluate changes, and will have many contentious debates and
bikeshedding.
It is unrealistic to develop revlog version 2 up front: there
are just too many uncertainties that we won't know until things
are implemented and experiments are run. Some changes will also
be invasive and prone to bit rot, so sitting on dozens of patches
is not practical.
This commit introduces skeleton support for version 2 revlogs in
a way that is flexible and not bound by backwards compatibility
concerns.
An experimental repo requirement for denoting revlog v2 has been
added. The requirement string has a sub-version component to it.
This will allow us to declare multiple requirements in the course
of developing revlog v2. Whenever we change the in-development
revlog v2 format, we can tweak the string, creating a new
requirement and locking out old clients. This will allow us to
make as many backwards incompatible changes and experiments to
revlog v2 as we want. In other words, we can land code and make
meaningful progress towards revlog v2 while still maintaining
extreme format flexibility up until the point we freeze the
format and remove the experimental labels.
To enable the new repo requirement, you must supply an experimental
and undocumented config option. But not just any boolean flag
will do: you need to explicitly use a value that no sane person
should ever type. This is an additional guard against enabling
revlog v2 on an installation it shouldn't be enabled on. The
specific scenario I'm trying to prevent is say a user with a
4.4 client with a frozen format enabling the option but then
downgrading to 4.3 and accidentally creating repos with an
outdated and unsupported repo format. Requiring a "challenge"
string should prevent this.
Because the format is not yet finalized and I don't want to take
any chances, revlog v2's version is currently 0xDEAD. I figure
squatting on a value we're likely never to use as an actual revlog
version to mean "internal testing only" is acceptable. And
"dead" is easily recognized as something meaningful.
There is a bunch of cleanup that is needed before work on revlog
v2 begins in earnest. I plan on doing that work once this patch
is accepted and we're comfortable with the idea of starting down
this path.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Fri, 19 May 2017 20:29:11 -0700 |
parents | 46ba2cdda476 |
children | fac9941bd542 |
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# Copyright 2006, 2007 Matt Mackall <mpm@selenic.com> # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. '''share a common history between several working directories Automatic Pooled Storage for Clones ----------------------------------- When this extension is active, :hg:`clone` can be configured to automatically share/pool storage across multiple clones. This mode effectively converts :hg:`clone` to :hg:`clone` + :hg:`share`. The benefit of using this mode is the automatic management of store paths and intelligent pooling of related repositories. The following ``share.`` config options influence this feature: ``share.pool`` Filesystem path where shared repository data will be stored. When defined, :hg:`clone` will automatically use shared repository storage instead of creating a store inside each clone. ``share.poolnaming`` How directory names in ``share.pool`` are constructed. "identity" means the name is derived from the first changeset in the repository. In this mode, different remotes share storage if their root/initial changeset is identical. In this mode, the local shared repository is an aggregate of all encountered remote repositories. "remote" means the name is derived from the source repository's path or URL. In this mode, storage is only shared if the path or URL requested in the :hg:`clone` command matches exactly to a repository that was cloned before. The default naming mode is "identity." ''' from __future__ import absolute_import import errno from mercurial.i18n import _ from mercurial import ( bookmarks, commands, error, extensions, hg, registrar, txnutil, util, ) repository = hg.repository parseurl = hg.parseurl 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 = 'ships-with-hg-core' @command('share', [('U', 'noupdate', None, _('do not create a working directory')), ('B', 'bookmarks', None, _('also share bookmarks')), ('', 'relative', None, _('point to source using a relative path ' '(EXPERIMENTAL)')), ], _('[-U] [-B] SOURCE [DEST]'), norepo=True) def share(ui, source, dest=None, noupdate=False, bookmarks=False, relative=False): """create a new shared repository Initialize a new repository and working directory that shares its history (and optionally bookmarks) with another repository. .. note:: using rollback or extensions that destroy/modify history (mq, rebase, etc.) can cause considerable confusion with shared clones. In particular, if two shared clones are both updated to the same changeset, and one of them destroys that changeset with rollback, the other clone will suddenly stop working: all operations will fail with "abort: working directory has unknown parent". The only known workaround is to use debugsetparents on the broken clone to reset it to a changeset that still exists. """ return hg.share(ui, source, dest=dest, update=not noupdate, bookmarks=bookmarks, relative=relative) @command('unshare', [], '') def unshare(ui, repo): """convert a shared repository to a normal one Copy the store data to the repo and remove the sharedpath data. """ if not repo.shared(): raise error.Abort(_("this is not a shared repo")) destlock = lock = None lock = repo.lock() try: # we use locks here because if we race with commit, we # can end up with extra data in the cloned revlogs that's # not pointed to by changesets, thus causing verify to # fail destlock = hg.copystore(ui, repo, repo.path) sharefile = repo.vfs.join('sharedpath') util.rename(sharefile, sharefile + '.old') repo.requirements.discard('shared') repo.requirements.discard('relshared') repo._writerequirements() finally: destlock and destlock.release() lock and lock.release() # update store, spath, svfs and sjoin of repo repo.unfiltered().__init__(repo.baseui, repo.root) # Wrap clone command to pass auto share options. def clone(orig, ui, source, *args, **opts): pool = ui.config('share', 'pool', None) if pool: pool = util.expandpath(pool) opts['shareopts'] = dict( pool=pool, mode=ui.config('share', 'poolnaming', 'identity'), ) return orig(ui, source, *args, **opts) def extsetup(ui): extensions.wrapfunction(bookmarks, '_getbkfile', getbkfile) extensions.wrapfunction(bookmarks.bmstore, 'recordchange', recordchange) extensions.wrapfunction(bookmarks.bmstore, '_writerepo', writerepo) extensions.wrapcommand(commands.table, 'clone', clone) def _hassharedbookmarks(repo): """Returns whether this repo has shared bookmarks""" try: shared = repo.vfs.read('shared').splitlines() except IOError as inst: if inst.errno != errno.ENOENT: raise return False return hg.sharedbookmarks in shared def _getsrcrepo(repo): """ Returns the source repository object for a given shared repository. If repo is not a shared repository, return None. """ if repo.sharedpath == repo.path: return None if util.safehasattr(repo, 'srcrepo') and repo.srcrepo: return repo.srcrepo # the sharedpath always ends in the .hg; we want the path to the repo source = repo.vfs.split(repo.sharedpath)[0] srcurl, branches = parseurl(source) srcrepo = repository(repo.ui, srcurl) repo.srcrepo = srcrepo return srcrepo def getbkfile(orig, repo): if _hassharedbookmarks(repo): srcrepo = _getsrcrepo(repo) if srcrepo is not None: # just orig(srcrepo) doesn't work as expected, because # HG_PENDING refers repo.root. try: fp, pending = txnutil.trypending(repo.root, repo.vfs, 'bookmarks') if pending: # only in this case, bookmark information in repo # is up-to-date. return fp fp.close() except IOError as inst: if inst.errno != errno.ENOENT: raise # otherwise, we should read bookmarks from srcrepo, # because .hg/bookmarks in srcrepo might be already # changed via another sharing repo repo = srcrepo # TODO: Pending changes in repo are still invisible in # srcrepo, because bookmarks.pending is written only into repo. # See also https://www.mercurial-scm.org/wiki/SharedRepository return orig(repo) def recordchange(orig, self, tr): # Continue with write to local bookmarks file as usual orig(self, tr) if _hassharedbookmarks(self._repo): srcrepo = _getsrcrepo(self._repo) if srcrepo is not None: category = 'share-bookmarks' tr.addpostclose(category, lambda tr: self._writerepo(srcrepo)) def writerepo(orig, self, repo): # First write local bookmarks file in case we ever unshare orig(self, repo) if _hassharedbookmarks(self._repo): srcrepo = _getsrcrepo(self._repo) if srcrepo is not None: orig(self, srcrepo)