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
$ cat > makepatch.py <<EOF
> import sys
> f = open(sys.argv[2], 'wb')
> w = f.write
> w(b'test message\n')
> w(b'diff --git a/a b/a\n')
> w(b'--- a/a\n')
> w(b'+++ b/a\n')
> w(b'@@ -1,5 +1,5 @@\n')
> w(b' a\n')
> w(b'-bbb\r\n')
> w(b'+yyyy\r\n')
> w(b' cc\r\n')
> w({'empty:lf': b' \n',
> 'empty:crlf': b' \r\n',
> 'empty:stripped-lf': b'\n',
> 'empty:stripped-crlf': b'\r\n'}[sys.argv[1]])
> w(b' d\n')
> w(b'-e\n')
> w(b'\\\\ No newline at end of file\n')
> w(b'+z\r\n')
> w(b'\\\\ No newline at end of file\r\n')
> EOF
$ hg init repo
$ cd repo
$ echo '\.diff' > .hgignore
Test different --eol values
$ "$PYTHON" -c 'open("a", "wb").write(b"a\nbbb\ncc\n\nd\ne")'
$ hg ci -Am adda
adding .hgignore
adding a
$ "$PYTHON" ../makepatch.py empty:lf eol.diff
$ "$PYTHON" ../makepatch.py empty:crlf eol-empty-crlf.diff
$ "$PYTHON" ../makepatch.py empty:stripped-lf eol-empty-stripped-lf.diff
$ "$PYTHON" ../makepatch.py empty:stripped-crlf eol-empty-stripped-crlf.diff
invalid eol
$ hg --config patch.eol='LFCR' import eol.diff
applying eol.diff
abort: unsupported line endings type: LFCR
[255]
$ hg revert -a
force LF
$ hg --traceback --config patch.eol='LF' import eol.diff
applying eol.diff
$ hg id
9e4ef7b3d4af tip
$ cat a
a
yyyy
cc
d
e (no-eol)
$ hg st
(test empty-line variants: all of them should generate the same revision)
$ hg up -qC 0
$ hg --config patch.eol='LF' import eol-empty-crlf.diff
applying eol-empty-crlf.diff
$ hg id
9e4ef7b3d4af tip
$ hg up -qC 0
$ hg --config patch.eol='LF' import eol-empty-stripped-lf.diff
applying eol-empty-stripped-lf.diff
$ hg id
9e4ef7b3d4af tip
$ hg up -qC 0
$ hg --config patch.eol='LF' import eol-empty-stripped-crlf.diff
applying eol-empty-stripped-crlf.diff
$ hg id
9e4ef7b3d4af tip
force CRLF
$ hg up -C 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg --traceback --config patch.eol='CRLF' import eol.diff
applying eol.diff
$ cat a
a\r (esc)
yyyy\r (esc)
cc\r (esc)
\r (esc)
d\r (esc)
e (no-eol)
$ hg st
auto EOL on LF file
$ hg up -C 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg --traceback --config patch.eol='auto' import eol.diff
applying eol.diff
$ cat a
a
yyyy
cc
d
e (no-eol)
$ hg st
auto EOL on CRLF file
$ "$PYTHON" -c 'open("a", "wb").write(b"a\r\nbbb\r\ncc\r\n\r\nd\r\ne")'
$ hg commit -m 'switch EOLs in a'
$ hg --traceback --config patch.eol='auto' import eol.diff
applying eol.diff
$ cat a
a\r (esc)
yyyy\r (esc)
cc\r (esc)
\r (esc)
d\r (esc)
e (no-eol)
$ hg st
auto EOL on new file or source without any EOL
$ "$PYTHON" -c 'open("noeol", "wb").write(b"noeol")'
$ hg add noeol
$ hg commit -m 'add noeol'
$ "$PYTHON" -c 'open("noeol", "wb").write(b"noeol\r\nnoeol\n")'
$ "$PYTHON" -c 'open("neweol", "wb").write(b"neweol\nneweol\r\n")'
$ hg add neweol
$ hg diff --git > noeol.diff
$ hg revert --no-backup noeol neweol
$ rm neweol
$ hg --traceback --config patch.eol='auto' import -m noeol noeol.diff
applying noeol.diff
$ cat noeol
noeol\r (esc)
noeol
$ cat neweol
neweol
neweol\r (esc)
$ hg st
Test --eol and binary patches
$ "$PYTHON" -c 'open("b", "wb").write(b"a\x00\nb\r\nd")'
$ hg ci -Am addb
adding b
$ "$PYTHON" -c 'open("b", "wb").write(b"a\x00\nc\r\nd")'
$ hg diff --git > bin.diff
$ hg revert --no-backup b
binary patch with --eol
$ hg import --config patch.eol='CRLF' -m changeb bin.diff
applying bin.diff
$ cat b
a\x00 (esc)
c\r (esc)
d (no-eol)
$ hg st
$ cd ..