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
Test the extensions.afterloaded() function
$ cat > foo.py <<EOF
> from mercurial import extensions
> def uisetup(ui):
> ui.write(b"foo.uisetup\\n")
> ui.flush()
> def bar_loaded(loaded):
> ui.write(b"foo: bar loaded: %r\\n" % (loaded,))
> ui.flush()
> extensions.afterloaded(b'bar', bar_loaded)
> EOF
$ cat > bar.py <<EOF
> def uisetup(ui):
> ui.write(b"bar.uisetup\\n")
> ui.flush()
> EOF
$ basepath=`pwd`
$ hg init basic
$ cd basic
$ echo foo > file
$ hg add file
$ hg commit -m 'add file'
$ echo '[extensions]' >> .hg/hgrc
$ echo "foo = $basepath/foo.py" >> .hg/hgrc
$ echo "bar = $basepath/bar.py" >> .hg/hgrc
$ hg log -r. -T'{rev}\n'
foo.uisetup
foo: bar loaded: True
bar.uisetup
0
Test afterloaded with the opposite extension load order
$ cd ..
$ hg init basic_reverse
$ cd basic_reverse
$ echo foo > file
$ hg add file
$ hg commit -m 'add file'
$ echo '[extensions]' >> .hg/hgrc
$ echo "bar = $basepath/bar.py" >> .hg/hgrc
$ echo "foo = $basepath/foo.py" >> .hg/hgrc
$ hg log -r. -T'{rev}\n'
bar.uisetup
foo.uisetup
foo: bar loaded: True
0
Test the extensions.afterloaded() function when the requested extension is not
loaded
$ cd ..
$ hg init notloaded
$ cd notloaded
$ echo foo > file
$ hg add file
$ hg commit -m 'add file'
$ echo '[extensions]' >> .hg/hgrc
$ echo "foo = $basepath/foo.py" >> .hg/hgrc
$ hg log -r. -T'{rev}\n'
foo.uisetup
foo: bar loaded: False
0
Test the extensions.afterloaded() function when the requested extension is not
configured but fails the minimum version check
$ cd ..
$ cat > minvers.py <<EOF
> minimumhgversion = b'9999.9999'
> def uisetup(ui):
> ui.write(b"minvers.uisetup\\n")
> ui.flush()
> EOF
$ hg init minversion
$ cd minversion
$ echo foo > file
$ hg add file
$ hg commit -m 'add file'
$ echo '[extensions]' >> .hg/hgrc
$ echo "foo = $basepath/foo.py" >> .hg/hgrc
$ echo "bar = $basepath/minvers.py" >> .hg/hgrc
$ hg log -r. -T'{rev}\n'
(third party extension bar requires version 9999.9999 or newer of Mercurial (current: *); disabling) (glob)
foo.uisetup
foo: bar loaded: False
0
Test the extensions.afterloaded() function when the requested extension is not
configured but fails the minimum version check, using the opposite load order
for the two extensions.
$ cd ..
$ hg init minversion_reverse
$ cd minversion_reverse
$ echo foo > file
$ hg add file
$ hg commit -m 'add file'
$ echo '[extensions]' >> .hg/hgrc
$ echo "bar = $basepath/minvers.py" >> .hg/hgrc
$ echo "foo = $basepath/foo.py" >> .hg/hgrc
$ hg log -r. -T'{rev}\n'
(third party extension bar requires version 9999.9999 or newer of Mercurial (current: *); disabling) (glob)
foo.uisetup
foo: bar loaded: False
0