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.
# pager.py - display output using a pager
#
# Copyright 2008 David Soria Parra <dsp@php.net>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
#
# To load the extension, add it to your configuration file:
#
# [extension]
# pager =
#
# Run "hg help pager" to get info on configuration.
'''browse command output with an external pager
To set the pager that should be used, set the application variable::
[pager]
pager = less -FRX
If no pager is set, the pager extensions uses the environment variable
$PAGER. If neither pager.pager, nor $PAGER is set, no pager is used.
You can disable the pager for certain commands by adding them to the
pager.ignore list::
[pager]
ignore = version, help, update
You can also enable the pager only for certain commands using
pager.attend. Below is the default list of commands to be paged::
[pager]
attend = annotate, cat, diff, export, glog, log, qdiff
Setting pager.attend to an empty value will cause all commands to be
paged.
If pager.attend is present, pager.ignore will be ignored.
Lastly, you can enable and disable paging for individual commands with
the attend-<command> option. This setting takes precedence over
existing attend and ignore options and defaults::
[pager]
attend-cat = false
To ignore global commands like :hg:`version` or :hg:`help`, you have
to specify them in your user configuration file.
The --pager=... option can also be used to control when the pager is
used. Use a boolean value like yes, no, on, off, or use auto for
normal behavior.
'''
import atexit, sys, os, signal, subprocess
from mercurial import commands, dispatch, util, extensions, cmdutil
from mercurial.i18n import _
# 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'
def _pagersubprocess(ui, p):
pager = subprocess.Popen(p, shell=True, bufsize=-1,
close_fds=util.closefds, stdin=subprocess.PIPE,
stdout=sys.stdout, stderr=sys.stderr)
stdout = os.dup(sys.stdout.fileno())
stderr = os.dup(sys.stderr.fileno())
os.dup2(pager.stdin.fileno(), sys.stdout.fileno())
if ui._isatty(sys.stderr):
os.dup2(pager.stdin.fileno(), sys.stderr.fileno())
@atexit.register
def killpager():
if util.safehasattr(signal, "SIGINT"):
signal.signal(signal.SIGINT, signal.SIG_IGN)
pager.stdin.close()
os.dup2(stdout, sys.stdout.fileno())
os.dup2(stderr, sys.stderr.fileno())
pager.wait()
def _runpager(ui, p):
_pagersubprocess(ui, p)
def uisetup(ui):
if '--debugger' in sys.argv or not ui.formatted():
return
def pagecmd(orig, ui, options, cmd, cmdfunc):
p = ui.config("pager", "pager", os.environ.get("PAGER"))
usepager = False
always = util.parsebool(options['pager'])
auto = options['pager'] == 'auto'
if not p:
pass
elif always:
usepager = True
elif not auto:
usepager = False
else:
attend = ui.configlist('pager', 'attend', attended)
ignore = ui.configlist('pager', 'ignore')
cmds, _ = cmdutil.findcmd(cmd, commands.table)
for cmd in cmds:
var = 'attend-%s' % cmd
if ui.config('pager', var):
usepager = ui.configbool('pager', var)
break
if (cmd in attend or
(cmd not in ignore and not attend)):
usepager = True
break
setattr(ui, 'pageractive', usepager)
if usepager:
ui.setconfig('ui', 'formatted', ui.formatted(), 'pager')
ui.setconfig('ui', 'interactive', False, 'pager')
if util.safehasattr(signal, "SIGPIPE"):
signal.signal(signal.SIGPIPE, signal.SIG_DFL)
_runpager(ui, p)
return orig(ui, options, cmd, cmdfunc)
# Wrap dispatch._runcommand after color is loaded so color can see
# ui.pageractive. Otherwise, if we loaded first, color's wrapped
# dispatch._runcommand would run without having access to ui.pageractive.
def afterloaded(loaded):
extensions.wrapfunction(dispatch, '_runcommand', pagecmd)
extensions.afterloaded('color', afterloaded)
def extsetup(ui):
commands.globalopts.append(
('', 'pager', 'auto',
_("when to paginate (boolean, always, auto, or never)"),
_('TYPE')))
attended = ['annotate', 'cat', 'diff', 'export', 'glog', 'log', 'qdiff']