Mercurial > hg
view hgext/relink.py @ 50336:cf4d2f31660d stable
chg: populate CHGHG if not set
Normally, chg determines which `hg` executable to use by first consulting the
`$CHGHG` and `$HG` environment variables, and if neither are present defaults
to the `hg` found in the user's `$PATH`. If built with the `HGPATHREL` compiler
flag, chg will instead assume that there exists an `hg` executable in the same
directory as the `chg` binary and attempt to use that.
This can cause problems in situations where there are multiple actively-used
Mercurial installations on the same system. When a `chg` client connects to a
running command server, the server process performs some basic validation to
determine whether a new command server needs to be spawned. These checks include
things like checking certain "sensitive" environment variables and config
sections, as well as checking whether the mtime of the extensions, hg's
`__version__.py` module, and the Python interpreter have changed.
Crucially, the command server doesn't explicitly check whether the executable it
is running from matches the executable that the `chg` client would have
otherwise invoked had there been no existing command server process. Without
`HGPATHREL`, this still gets implicitly checked during the validation step,
because the only way to specify an alternate hg executable (apart from `$PATH`)
is via the `$CHGHG` and `$HG` environment variables, both of which are checked.
With `HGPATHREL`, however, the command server has no way of knowing which hg
executable the client would have run. This means that a client located at
`/version_B/bin/chg` will happily connect to a command server running
`/version_A/bin/hg` instead of `/version_B/bin/hg` as expected. A simple
solution is to have the client set `$CHGHG` itself, which then allows the
command server's environment validation to work as intended.
I have tested this manually using two locally built hg installations and it
seems to work with no ill effects. That said, I'm not sure how to write an
automated test for this since the `chg` available to the tests isn't even built
with the `HGPATHREL` compiler flag to begin with.
author | Arun Kulshreshtha <akulshreshtha@janestreet.com> |
---|---|
date | Mon, 27 Mar 2023 17:30:14 -0400 |
parents | c6ae90515660 |
children | d28cc52e2c0f |
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# Mercurial extension to provide 'hg relink' command # # Copyright (C) 2007 Brendan Cully <brendan@kublai.com> # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. """recreates hardlinks between repository clones""" import os import stat from mercurial.i18n import _ from mercurial.pycompat import open from mercurial import ( error, hg, registrar, util, ) from mercurial.utils import ( stringutil, urlutil, ) 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'relink', [], _(b'[ORIGIN]'), helpcategory=command.CATEGORY_MAINTENANCE ) def relink(ui, repo, origin=None, **opts): """recreate hardlinks between two repositories When repositories are cloned locally, their data files will be hardlinked so that they only use the space of a single repository. Unfortunately, subsequent pulls into either repository will break hardlinks for any files touched by the new changesets, even if both repositories end up pulling the same changes. Similarly, passing --rev to "hg clone" will fail to use any hardlinks, falling back to a complete copy of the source repository. This command lets you recreate those hardlinks and reclaim that wasted space. This repository will be relinked to share space with ORIGIN, which must be on the same local disk. If ORIGIN is omitted, looks for "default-relink", then "default", in [paths]. Do not attempt any read operations on this repository while the command is running. (Both repositories will be locked against writes.) """ if not util.safehasattr(util, b'samefile') or not util.safehasattr( util, b'samedevice' ): raise error.Abort(_(b'hardlinks are not supported on this system')) if origin is None and b'default-relink' in ui.paths: origin = b'default-relink' path = urlutil.get_unique_pull_path_obj(b'relink', ui, origin) src = hg.repository(repo.baseui, path.loc) ui.status(_(b'relinking %s to %s\n') % (src.store.path, repo.store.path)) if repo.root == src.root: ui.status(_(b'there is nothing to relink\n')) return if not util.samedevice(src.store.path, repo.store.path): # No point in continuing raise error.Abort(_(b'source and destination are on different devices')) with repo.lock(), src.lock(): candidates = sorted(collect(src, ui)) targets = prune(candidates, src.store.path, repo.store.path, ui) do_relink(src.store.path, repo.store.path, targets, ui) def collect(src, ui): seplen = len(os.path.sep) candidates = [] live = len(src[b'tip'].manifest()) # Your average repository has some files which were deleted before # the tip revision. We account for that by assuming that there are # 3 tracked files for every 2 live files as of the tip version of # the repository. # # mozilla-central as of 2010-06-10 had a ratio of just over 7:5. total = live * 3 // 2 src = src.store.path progress = ui.makeprogress(_(b'collecting'), unit=_(b'files'), total=total) pos = 0 ui.status( _(b"tip has %d files, estimated total number of files: %d\n") % (live, total) ) for dirpath, dirnames, filenames in os.walk(src): dirnames.sort() relpath = dirpath[len(src) + seplen :] for filename in sorted(filenames): if filename[-2:] not in (b'.d', b'.i'): continue st = os.stat(os.path.join(dirpath, filename)) if not stat.S_ISREG(st.st_mode): continue pos += 1 candidates.append((os.path.join(relpath, filename), st)) progress.update(pos, item=filename) progress.complete() ui.status(_(b'collected %d candidate storage files\n') % len(candidates)) return candidates def prune(candidates, src, dst, ui): def linkfilter(src, dst, st): try: ts = os.stat(dst) except OSError: # Destination doesn't have this file? return False if util.samefile(src, dst): return False if not util.samedevice(src, dst): # No point in continuing raise error.Abort( _(b'source and destination are on different devices') ) if st.st_size != ts.st_size: return False return st targets = [] progress = ui.makeprogress( _(b'pruning'), unit=_(b'files'), total=len(candidates) ) pos = 0 for fn, st in candidates: pos += 1 srcpath = os.path.join(src, fn) tgt = os.path.join(dst, fn) ts = linkfilter(srcpath, tgt, st) if not ts: ui.debug(b'not linkable: %s\n' % fn) continue targets.append((fn, ts.st_size)) progress.update(pos, item=fn) progress.complete() ui.status( _(b'pruned down to %d probably relinkable files\n') % len(targets) ) return targets def do_relink(src, dst, files, ui): def relinkfile(src, dst): bak = dst + b'.bak' os.rename(dst, bak) try: util.oslink(src, dst) except OSError: os.rename(bak, dst) raise os.remove(bak) CHUNKLEN = 65536 relinked = 0 savedbytes = 0 progress = ui.makeprogress( _(b'relinking'), unit=_(b'files'), total=len(files) ) pos = 0 for f, sz in files: pos += 1 source = os.path.join(src, f) tgt = os.path.join(dst, f) # Binary mode, so that read() works correctly, especially on Windows sfp = open(source, b'rb') dfp = open(tgt, b'rb') sin = sfp.read(CHUNKLEN) while sin: din = dfp.read(CHUNKLEN) if sin != din: break sin = sfp.read(CHUNKLEN) sfp.close() dfp.close() if sin: ui.debug(b'not linkable: %s\n' % f) continue try: relinkfile(source, tgt) progress.update(pos, item=f) relinked += 1 savedbytes += sz except OSError as inst: ui.warn(b'%s: %s\n' % (tgt, stringutil.forcebytestr(inst))) progress.complete() ui.status( _(b'relinked %d files (%s reclaimed)\n') % (relinked, util.bytecount(savedbytes)) )