bisect: avoid copying ancestor list for non-merge commits
During a bisection, hg needs to compute a list of all ancestors for every
candidate commit. This is accomplished via a bottom-up traversal of the set of
candidates, during which each revision's ancestor list is populated using the
ancestor list of its parent(s). Previously, this involved copying the entire
list, which could be very long in if the bisection range was large.
To help improve this, we can observe that each candidate commit is visited
exactly once, at which point its ancestor list is copied into its children's
lists and then dropped. In the case of non-merge commits, a commit's ancestor
list consists exactly of its parent's list plus itself. This means that we can
trivially reuse the parent's existing list for one of its non-merge children,
which avoids copying entirely if that commit is the parent's only child. This
makes bisections over linear ranges of commits much faster.
During some informal testing in the large publicly-available `mozilla-central`
repository, this noticeably sped up bisections over large ranges of history:
Setup:
$ cd mozilla-central
$ hg bisect --reset
$ hg bisect --good 0
$ hg log -r tip -T '{rev}\n'
628417
Test:
$ time hg bisect --bad tip --noupdate
Before:
real 3m35.927s
user 3m35.553s
sys 0m0.319s
After:
real 1m41.142s
user 1m40.810s
sys 0m0.285s
#require test-repo slow osx osxpackaging
$ . "$TESTDIR/helpers-testrepo.sh"
$ testrepohgenv
$ OUTPUTDIR="`pwd`"
$ export OUTPUTDIR
$ KEEPMPKG=yes
$ export KEEPMPKG
$ cd "$TESTDIR"/..
$ contrib/genosxversion.py --selftest ignoredarg
$ make osx > "$OUTPUTDIR/build.log" 2>&1
$ cd "$OUTPUTDIR"
$ ls -d *.pkg
Mercurial-*-macosx10.*.pkg (glob)
$ xar -xf Mercurial*.pkg
Gather list of all installed files:
$ lsbom mercurial.pkg/Bom > boms.txt
We've had problems with the filter logic in the past. Make sure no
.DS_Store files ended up in the final package:
$ grep DS_S boms.txt
[1]
Spot-check some randomly selected files:
$ grep bdiff boms.txt | cut -d ' ' -f 1,2,3
./Library/Python/2.7/site-packages/mercurial/cext/bdiff.so 100755 0/0
./Library/Python/2.7/site-packages/mercurial/cffi/bdiff.py 100644 0/0
./Library/Python/2.7/site-packages/mercurial/cffi/bdiff.pyc 100644 0/0
./Library/Python/2.7/site-packages/mercurial/cffi/bdiff.pyo 100644 0/0
./Library/Python/2.7/site-packages/mercurial/cffi/bdiffbuild.py 100644 0/0
./Library/Python/2.7/site-packages/mercurial/cffi/bdiffbuild.pyc 100644 0/0
./Library/Python/2.7/site-packages/mercurial/cffi/bdiffbuild.pyo 100644 0/0
./Library/Python/2.7/site-packages/mercurial/pure/bdiff.py 100644 0/0
./Library/Python/2.7/site-packages/mercurial/pure/bdiff.pyc 100644 0/0
./Library/Python/2.7/site-packages/mercurial/pure/bdiff.pyo 100644 0/0
$ grep zsh/site-functions/_hg boms.txt | cut -d ' ' -f 1,2,3
./usr/local/share/zsh/site-functions/_hg 100644 0/0
$ grep bash-completion/completions/hg boms.txt | cut -d ' ' -f 1,2,3
./usr/local/share/bash-completion-completions/hg 100644 0/0
$ egrep 'man[15]' boms.txt | cut -d ' ' -f 1,2,3
./usr/local/share/man/man1 40755 0/0
./usr/local/share/man/man1/chg.1 100644 0/0
./usr/local/share/man/man1/hg.1 100644 0/0
./usr/local/share/man/man5 40755 0/0
./usr/local/share/man/man5/hgignore.5 100644 0/0
./usr/local/share/man/man5/hgrc.5 100644 0/0
$ grep bser boms.txt | cut -d ' ' -f 1,2,3
./Library/Python/2.7/site-packages/hgext/fsmonitor/pywatchman/bser.so 100755 0/0
./Library/Python/2.7/site-packages/hgext/fsmonitor/pywatchman/pybser.py 100644 0/0
./Library/Python/2.7/site-packages/hgext/fsmonitor/pywatchman/pybser.pyc 100644 0/0
./Library/Python/2.7/site-packages/hgext/fsmonitor/pywatchman/pybser.pyo 100644 0/0
$ grep localrepo boms.txt | cut -d ' ' -f 1,2,3
./Library/Python/2.7/site-packages/mercurial/localrepo.py 100644 0/0
./Library/Python/2.7/site-packages/mercurial/localrepo.pyc 100644 0/0
./Library/Python/2.7/site-packages/mercurial/localrepo.pyo 100644 0/0
$ egrep 'bin/' boms.txt | cut -d ' ' -f 1,2,3
./usr/local/bin/chg 100755 0/0
./usr/local/bin/hg 100755 0/0
Make sure the built binary uses the system Python interpreter
$ bsdtar xf mercurial.pkg/Payload usr/local/bin
Use a glob to find this to avoid check-code whining about a fixed path.
$ head -n 1 usr/local/b?n/hg
#!/System/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python
Note that we're not currently installing any /etc/mercurial stuff,
including merge-tool configurations.