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 >> $HGRCPATH <<EOF
> [extensions]
> rebase=
>
> [alias]
> tglog = log -G --template "{rev}: {node|short} '{desc}'\n"
>
> [extensions]
> drawdag=$TESTDIR/drawdag.py
> EOF
Rebasing D onto B detaching from C (one commit):
$ hg init a1
$ cd a1
$ hg debugdrawdag <<EOF
> D
> |
> C B
> |/
> A
> EOF
$ hg phase --force --secret D
$ hg rebase -s D -d B
rebasing 3:e7b3f00ed42e D tip "D"
saved backup bundle to $TESTTMP/a1/.hg/strip-backup/e7b3f00ed42e-6f368371-rebase.hg
$ hg log -G --template "{rev}:{phase} '{desc}' {branches}\n"
o 3:secret 'D'
|
| o 2:draft 'C'
| |
o | 1:draft 'B'
|/
o 0:draft 'A'
$ hg manifest --rev tip
A
B
D
$ cd ..
Rebasing D onto B detaching from C (two commits):
$ hg init a2
$ cd a2
$ hg debugdrawdag <<EOF
> E
> |
> D
> |
> C B
> |/
> A
> EOF
$ hg rebase -s D -d B
rebasing 3:e7b3f00ed42e D "D"
rebasing 4:69a34c08022a E tip "E"
saved backup bundle to $TESTTMP/a2/.hg/strip-backup/e7b3f00ed42e-a2ec7cea-rebase.hg
$ hg tglog
o 4: ee79e0744528 'E'
|
o 3: 10530e1d72d9 'D'
|
| o 2: dc0947a82db8 'C'
| |
o | 1: 112478962961 'B'
|/
o 0: 426bada5c675 'A'
$ hg manifest --rev tip
A
B
D
E
$ cd ..
Rebasing C onto B using detach (same as not using it):
$ hg init a3
$ cd a3
$ hg debugdrawdag <<EOF
> D
> |
> C B
> |/
> A
> EOF
$ hg rebase -s C -d B
rebasing 2:dc0947a82db8 C "C"
rebasing 3:e7b3f00ed42e D tip "D"
saved backup bundle to $TESTTMP/a3/.hg/strip-backup/dc0947a82db8-b8481714-rebase.hg
$ hg tglog
o 3: 7375f3dbfb0f 'D'
|
o 2: bbfdd6cb49aa 'C'
|
o 1: 112478962961 'B'
|
o 0: 426bada5c675 'A'
$ hg manifest --rev tip
A
B
C
D
$ cd ..
Rebasing D onto B detaching from C and collapsing:
$ hg init a4
$ cd a4
$ hg debugdrawdag <<EOF
> E
> |
> D
> |
> C B
> |/
> A
> EOF
$ hg phase --force --secret E
$ hg rebase --collapse -s D -d B
rebasing 3:e7b3f00ed42e D "D"
rebasing 4:69a34c08022a E tip "E"
saved backup bundle to $TESTTMP/a4/.hg/strip-backup/e7b3f00ed42e-a2ec7cea-rebase.hg
$ hg log -G --template "{rev}:{phase} '{desc}' {branches}\n"
o 3:secret 'Collapsed revision
| * D
| * E'
| o 2:draft 'C'
| |
o | 1:draft 'B'
|/
o 0:draft 'A'
$ hg manifest --rev tip
A
B
D
E
$ cd ..
Rebasing across null as ancestor
$ hg init a5
$ cd a5
$ hg debugdrawdag <<EOF
> E
> |
> D
> |
> C
> |
> A B
> EOF
$ hg rebase -s C -d B
rebasing 2:dc0947a82db8 C "C"
rebasing 3:e7b3f00ed42e D "D"
rebasing 4:69a34c08022a E tip "E"
saved backup bundle to $TESTTMP/a5/.hg/strip-backup/dc0947a82db8-3eefec98-rebase.hg
$ hg tglog
o 4: e3d0c70d606d 'E'
|
o 3: e9153d36a1af 'D'
|
o 2: a7ac28b870a8 'C'
|
o 1: fc2b737bb2e5 'B'
o 0: 426bada5c675 'A'
$ hg rebase -d 1 -s 3
rebasing 3:e9153d36a1af "D"
rebasing 4:e3d0c70d606d tip "E"
saved backup bundle to $TESTTMP/a5/.hg/strip-backup/e9153d36a1af-db7388ed-rebase.hg
$ hg tglog
o 4: 2c24e540eccd 'E'
|
o 3: 73f786ed52ff 'D'
|
| o 2: a7ac28b870a8 'C'
|/
o 1: fc2b737bb2e5 'B'
o 0: 426bada5c675 'A'
$ cd ..
Verify that target is not selected as external rev (issue3085)
$ hg init a6
$ cd a6
$ hg debugdrawdag <<EOF
> H
> | G
> |/|
> F E
> |/
> A
> EOF
$ hg up -q G
$ echo "I" >> E
$ hg ci -m "I"
$ hg tag --local I
$ hg merge H
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -m "Merge"
$ echo "J" >> F
$ hg ci -m "J"
$ hg tglog
@ 7: c6aaf0d259c0 'J'
|
o 6: 0cfbc7e8faaf 'Merge'
|\
| o 5: b92d164ad3cb 'I'
| |
o | 4: 4ea5b230dea3 'H'
| |
| o 3: c6001eacfde5 'G'
|/|
o | 2: 8908a377a434 'F'
| |
| o 1: 7fb047a69f22 'E'
|/
o 0: 426bada5c675 'A'
$ hg rebase -s I -d H --collapse --config ui.merge=internal:other
rebasing 5:b92d164ad3cb I "I"
rebasing 6:0cfbc7e8faaf "Merge"
rebasing 7:c6aaf0d259c0 tip "J"
saved backup bundle to $TESTTMP/a6/.hg/strip-backup/b92d164ad3cb-88fd7ab7-rebase.hg
$ hg tglog
@ 5: 65079693dac4 'Collapsed revision
| * I
| * Merge
| * J'
o 4: 4ea5b230dea3 'H'
|
| o 3: c6001eacfde5 'G'
|/|
o | 2: 8908a377a434 'F'
| |
| o 1: 7fb047a69f22 'E'
|/
o 0: 426bada5c675 'A'
$ hg log --rev tip
changeset: 5:65079693dac4
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Collapsed revision
$ cd ..
Ensure --continue restores a correct state (issue3046) and phase:
$ hg init a7
$ cd a7
$ hg debugdrawdag <<EOF
> C B
> |/
> A
> EOF
$ hg up -q C
$ echo 'B2' > B
$ hg ci -A -m 'B2'
adding B
$ hg phase --force --secret .
$ hg rebase -s . -d B --config ui.merge=internal:merge
rebasing 3:17b4880d2402 tip "B2"
merging B
warning: conflicts while merging B! (edit, then use 'hg resolve --mark')
unresolved conflicts (see 'hg resolve', then 'hg rebase --continue')
[240]
$ hg resolve --all -t internal:local
(no more unresolved files)
continue: hg rebase --continue
$ hg rebase -c
rebasing 3:17b4880d2402 tip "B2"
note: not rebasing 3:17b4880d2402 tip "B2", its destination already has all its changes
saved backup bundle to $TESTTMP/a7/.hg/strip-backup/17b4880d2402-1ae1f6cc-rebase.hg
$ hg log -G --template "{rev}:{phase} '{desc}' {branches}\n"
o 2:draft 'C'
|
| @ 1:draft 'B'
|/
o 0:draft 'A'
$ cd ..