share: provide a more useful text for hg help

Differential Revision: https://phab.mercurial-scm.org/D8651

hgext/share.py

@@ -1,203 +1,212 b''
 # Copyright 2006, 2007 Matt Mackall <[e-mail]>
 #
 # 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
 
+The share extension introduces a new command :hg:`share` to create a new
+working directory. This is similar to :hg:`clone`, but doesn't involve
+copying or linking the storage of the repository. This allows working on
+different branches or changes in parallel without the associated cost in
+terms of disk space.
+
+Note: destructive operations or extensions like :hg:`rollback` should be
+used with care as they can result in confusing problems.
+
 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,
 )
 
 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'share',
     [
         (b'U', b'noupdate', None, _(b'do not create a working directory')),
         (b'B', b'bookmarks', None, _(b'also share bookmarks')),
         (b'', b'relative', None, _(b'point to source using a relative path'),),
     ],
     _(b'[-U] [-B] SOURCE [DEST]'),
     helpcategory=command.CATEGORY_REPO_CREATION,
     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.
     """
 
     hg.share(
         ui,
         source,
         dest=dest,
         update=not noupdate,
         bookmarks=bookmarks,
         relative=relative,
     )
     return 0
 
 
 @command(b'unshare', [], b'', helpcategory=command.CATEGORY_MAINTENANCE)
 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(_(b"this is not a shared repo"))
 
     hg.unshare(ui, repo)
 
 
 # Wrap clone command to pass auto share options.
 def clone(orig, ui, source, *args, **opts):
     pool = ui.config(b'share', b'pool')
     if pool:
         pool = util.expandpath(pool)
 
     opts['shareopts'] = {
         b'pool': pool,
         b'mode': ui.config(b'share', b'poolnaming'),
     }
 
     return orig(ui, source, *args, **opts)
 
 
 def extsetup(ui):
     extensions.wrapfunction(bookmarks, b'_getbkfile', getbkfile)
     extensions.wrapfunction(bookmarks.bmstore, b'_recordchange', recordchange)
     extensions.wrapfunction(bookmarks.bmstore, b'_writerepo', writerepo)
     extensions.wrapcommand(commands.table, b'clone', clone)
 
 
 def _hassharedbookmarks(repo):
     """Returns whether this repo has shared bookmarks"""
     if bookmarks.bookmarksinstore(repo):
         # Kind of a lie, but it means that we skip our custom reads and writes
         # from/to the source repo.
         return False
     try:
         shared = repo.vfs.read(b'shared').splitlines()
     except IOError as inst:
         if inst.errno != errno.ENOENT:
             raise
         return False
     return hg.sharedbookmarks in shared
 
 
 def getbkfile(orig, repo):
     if _hassharedbookmarks(repo):
         srcrepo = hg.sharedreposource(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, b'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 = hg.sharedreposource(self._repo)
         if srcrepo is not None:
             category = b'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 = hg.sharedreposource(self._repo)
         if srcrepo is not None:
             orig(self, srcrepo)