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 'hg log' with a bookmark
Create the repository
$ hg init Test-D8973
$ cd Test-D8973
$ echo "bar" > foo.txt
$ hg add foo.txt
$ hg commit -m "Add foo in 'default'"
Add a bookmark for topic X
$ hg branch -f sebhtml
marked working directory as branch sebhtml
(branches are permanent and global, did you want a bookmark?)
$ hg bookmark sebhtml/99991-topic-X
$ hg up sebhtml/99991-topic-X
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo "X" > x.txt
$ hg add x.txt
$ hg commit -m "Add x.txt in 'sebhtml/99991-topic-X'"
$ hg log -B sebhtml/99991-topic-X
changeset: 1:29f39dea9bf9
branch: sebhtml
bookmark: sebhtml/99991-topic-X
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Add x.txt in 'sebhtml/99991-topic-X'
Add a bookmark for topic Y
$ hg update default
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
(leaving bookmark sebhtml/99991-topic-X)
$ echo "Y" > y.txt
$ hg add y.txt
$ hg branch -f sebhtml
marked working directory as branch sebhtml
$ hg bookmark sebhtml/99992-topic-Y
$ hg up sebhtml/99992-topic-Y
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg commit -m "Add y.txt in 'sebhtml/99992-topic-Y'"
created new head
$ hg log -B sebhtml/99992-topic-Y
changeset: 2:11df7969cf8d
branch: sebhtml
bookmark: sebhtml/99992-topic-Y
tag: tip
parent: 0:eaea25376a59
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Add y.txt in 'sebhtml/99992-topic-Y'
The log of topic Y does not interfere with the log of topic X
$ hg log -B sebhtml/99991-topic-X
changeset: 1:29f39dea9bf9
branch: sebhtml
bookmark: sebhtml/99991-topic-X
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Add x.txt in 'sebhtml/99991-topic-X'
Merge topics Y and X in the default branch
$ hg update default
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
(leaving bookmark sebhtml/99992-topic-Y)
$ hg bookmark
sebhtml/99991-topic-X 1:29f39dea9bf9
sebhtml/99992-topic-Y 2:11df7969cf8d
$ hg merge sebhtml/99992-topic-Y
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg commit -m "Merge branch 'sebhtml/99992-topic-Y' into 'default'"
$ hg update default
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg merge sebhtml/99991-topic-X
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg commit -m "Merge branch 'sebhtml/99991-topic-X' into 'default'"
Check the log of topic X, topic Y, and default branch
$ hg log -B sebhtml/99992-topic-Y
$ hg log -B sebhtml/99991-topic-X
$ hg log -b default
changeset: 4:c26ba8c1e1cb
tag: tip
parent: 3:2189f3fb90d6
parent: 1:29f39dea9bf9
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Merge branch 'sebhtml/99991-topic-X' into 'default'
changeset: 3:2189f3fb90d6
parent: 0:eaea25376a59
parent: 2:11df7969cf8d
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Merge branch 'sebhtml/99992-topic-Y' into 'default'
changeset: 0:eaea25376a59
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: Add foo in 'default'
Set up multiple bookmarked heads:
$ hg bookmark merged-head
$ hg up 1
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
(leaving bookmark merged-head)
$ echo "Z" > z.txt
$ hg ci -Am 'Add Z'
adding z.txt
$ hg bookmark topic-Z
$ hg log -GT '{rev}: {branch}, {bookmarks}\n'
@ 5: sebhtml, topic-Z
|
| o 4: default, merged-head
|/|
| o 3: default,
| |\
| | o 2: sebhtml, sebhtml/99992-topic-Y
| |/
o | 1: sebhtml, sebhtml/99991-topic-X
|/
o 0: default,
Multiple revisions under bookmarked head:
$ hg log -GT '{rev}: {branch}, {bookmarks}\n' -B merged-head
o 4: default, merged-head
|\
| ~
o 3: default,
|\
~ ~
Follows multiple bookmarks:
$ hg log -GT '{rev}: {branch}, {bookmarks}\n' -B merged-head -B topic-Z
@ 5: sebhtml, topic-Z
|
~
o 4: default, merged-head
|\
| ~
o 3: default,
|\
~ ~
Filter by bookmark and branch:
$ hg log -GT '{rev}: {branch}, {bookmarks}\n' -B merged-head -B topic-Z -b default
o 4: default, merged-head
|\
| ~
o 3: default,
|\
~ ~
Unknown bookmark:
$ hg log -B unknown
abort: bookmark 'unknown' does not exist
[10]
Shouldn't accept string-matcher syntax:
$ hg log -B 're:.*'
abort: bookmark 're:.*' does not exist
[10]