revlog: change generaldelta delta parent heuristic
The old generaldelta heuristic was "if p1 (or p2) was closer than the last full text,
use it, otherwise use prev". This was problematic when a repo contained multiple
branches that were very different. If commits to branch A were pushed, and the
last full text was branch B, it would generate a fulltext. Then if branch B was
pushed, it would generate another fulltext. The problem is that the last
fulltext (and delta'ing against `prev` in general) has no correlation with the
contents of the incoming revision, and therefore will always have degenerate
cases.
According to the blame, that algorithm was chosen to minimize the chain length.
Since there is already code that protects against that (the delta-vs-fulltext
code), and since it has been improved since the original generaldelta algorithm
went in (2011), I believe the chain length criteria will still be preserved.
The new algorithm always diffs against p1 (or p2 if it's closer), unless the
resulting delta will fail the delta-vs-fulltext check, in which case we delta
against prev.
Some before and after stats on manifest.d size.
internal large repo
old heuristic - 2.0 GB
new heuristic - 1.2 GB
mozilla-central
old heuristic - 242 MB
new heuristic - 261 MB
The regression in mozilla central is due to the new heuristic choosing p2r as
the delta when it's closer to the tip. Switching the algorithm to always prefer
p1r brings the size back down (242 MB). This is result of the way in which
mozilla does merges and pushes, and the result could easily swing the other
direction in other repos (depending on if they merge X into Y or Y into X), but
will never be as degenerate as before.
I future patch will address the regression by introducing an optional, even more
aggressive delta heuristic which will knock the mozilla manifest size down
dramatically.
# Copyright (C) 2006 - Marco Barisione <marco@barisione.org>
#
# This is a small extension for Mercurial (http://mercurial.selenic.com/)
# that removes files not known to mercurial
#
# This program was inspired by the "cvspurge" script contained in CVS
# utilities (http://www.red-bean.com/cvsutils/).
#
# For help on the usage of "hg purge" use:
# hg help purge
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, see <http://www.gnu.org/licenses/>.
'''command to delete untracked files from the working directory'''
from mercurial import util, commands, cmdutil, scmutil
from mercurial.i18n import _
import os
cmdtable = {}
command = cmdutil.command(cmdtable)
# Note for extension authors: ONLY specify testedwith = 'internal' 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 = 'internal'
@command('purge|clean',
[('a', 'abort-on-err', None, _('abort if an error occurs')),
('', 'all', None, _('purge ignored files too')),
('', 'dirs', None, _('purge empty directories')),
('', 'files', None, _('purge files')),
('p', 'print', None, _('print filenames instead of deleting them')),
('0', 'print0', None, _('end filenames with NUL, for use with xargs'
' (implies -p/--print)')),
] + commands.walkopts,
_('hg purge [OPTION]... [DIR]...'))
def purge(ui, repo, *dirs, **opts):
'''removes files not tracked by Mercurial
Delete files not known to Mercurial. This is useful to test local
and uncommitted changes in an otherwise-clean source tree.
This means that purge will delete the following by default:
- Unknown files: files marked with "?" by :hg:`status`
- Empty directories: in fact Mercurial ignores directories unless
they contain files under source control management
But it will leave untouched:
- Modified and unmodified tracked files
- Ignored files (unless --all is specified)
- New files added to the repository (with :hg:`add`)
The --files and --dirs options can be used to direct purge to delete
only files, only directories, or both. If neither option is given,
both will be deleted.
If directories are given on the command line, only files in these
directories are considered.
Be careful with purge, as you could irreversibly delete some files
you forgot to add to the repository. If you only want to print the
list of files that this program would delete, use the --print
option.
'''
act = not opts['print']
eol = '\n'
if opts['print0']:
eol = '\0'
act = False # --print0 implies --print
removefiles = opts['files']
removedirs = opts['dirs']
if not removefiles and not removedirs:
removefiles = True
removedirs = True
def remove(remove_func, name):
if act:
try:
remove_func(repo.wjoin(name))
except OSError:
m = _('%s cannot be removed') % name
if opts['abort_on_err']:
raise util.Abort(m)
ui.warn(_('warning: %s\n') % m)
else:
ui.write('%s%s' % (name, eol))
match = scmutil.match(repo[None], dirs, opts)
if removedirs:
directories = []
match.explicitdir = match.traversedir = directories.append
status = repo.status(match=match, ignored=opts['all'], unknown=True)
if removefiles:
for f in sorted(status.unknown + status.ignored):
if act:
ui.note(_('removing file %s\n') % f)
remove(util.unlink, f)
if removedirs:
for f in sorted(directories, reverse=True):
if match(f) and not os.listdir(repo.wjoin(f)):
if act:
ui.note(_('removing directory %s\n') % f)
remove(os.rmdir, f)