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revlog: change generaldelta delta parent heuristic...
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.

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simplemerge
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Alexis S. L. Carvalho
actually port simplemerge to hg...
r4363 #!/usr/bin/env python
Alexis S. L. Carvalho
Import 3-way merge code from bzr...
r4362
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 from mercurial import demandimport
demandimport.enable()
Alexis S. L. Carvalho
Import 3-way merge code from bzr...
r4362
Simon Heimberg
cleanup: drop unused variables and an unused import
r19378 import sys
Alexis S. L. Carvalho
actually port simplemerge to hg...
r4363 from mercurial.i18n import _
Steve Borho
simplemerge: use ui.warn() for warnings
r8269 from mercurial import simplemerge, fancyopts, util, ui
Alexis S. L. Carvalho
Import 3-way merge code from bzr...
r4362
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 options = [('L', 'label', [], _('labels to use on conflict markers')),
('a', 'text', None, _('treat all files as text')),
('p', 'print', None,
_('print results instead of overwriting LOCAL')),
Pierre-Yves David
simplemerge: burn "minimal" feature to the ground...
r22023 ('', 'no-minimal', None, _('no effect (DEPRECATED)')),
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 ('h', 'help', None, _('display help and exit')),
('q', 'quiet', None, _('suppress output'))]
usage = _('''simplemerge [OPTS] LOCAL BASE OTHER
Simple three-way file merge utility with a minimal feature set.
Thomas Arendsen Hein
Remove trailing spaces
r5081
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 Apply to LOCAL the changes necessary to go from BASE to OTHER.
Thomas Arendsen Hein
Remove trailing spaces
r5081
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 By default, LOCAL is overwritten with the results of this operation.
''')
Matt Mackall
merge: move the bulk of simplemerge into core...
r6002 class ParseError(Exception):
"""Exception raised on errors in parsing the command line."""
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 def showhelp():
sys.stdout.write(usage)
sys.stdout.write('\noptions:\n')
Alexis S. L. Carvalho
Import 3-way merge code from bzr...
r4362
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 out_opts = []
for shortopt, longopt, default, desc in options:
out_opts.append(('%2s%s' % (shortopt and '-%s' % shortopt,
longopt and ' --%s' % longopt),
'%s' % desc))
opts_len = max([len(opt[0]) for opt in out_opts])
for first, second in out_opts:
sys.stdout.write(' %-*s %s\n' % (opts_len, first, second))
Matt Mackall
merge: move the bulk of simplemerge into core...
r6002 try:
Patrick Mezard
tests: Windows compatibility fixes...
r7080 for fp in (sys.stdin, sys.stdout, sys.stderr):
Adrian Buehlmann
rename util.set_binary to setbinary
r14233 util.setbinary(fp)
Mads Kiilerich
tests: run check-code on Python files without .py extension
r19022
Matt Mackall
merge: move the bulk of simplemerge into core...
r6002 opts = {}
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 try:
Matt Mackall
merge: move the bulk of simplemerge into core...
r6002 args = fancyopts.fancyopts(sys.argv[1:], options, opts)
except fancyopts.getopt.GetoptError, e:
raise ParseError(e)
if opts['help']:
Alexis S. L. Carvalho
polish the simplemerge command; add a test
r4364 showhelp()
Matt Mackall
merge: move the bulk of simplemerge into core...
r6002 sys.exit(0)
if len(args) != 3:
raise ParseError(_('wrong number of arguments'))
Steve Borho
simplemerge: use ui.warn() for warnings
r8269 sys.exit(simplemerge.simplemerge(ui.ui(), *args, **opts))
Matt Mackall
merge: move the bulk of simplemerge into core...
r6002 except ParseError, e:
sys.stdout.write("%s: %s\n" % (sys.argv[0], e))
showhelp()
sys.exit(1)
except util.Abort, e:
sys.stderr.write("abort: %s\n" % e)
sys.exit(255)
except KeyboardInterrupt:
sys.exit(255)