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 for old histedit issue #6:
editing a changeset without any actual change would corrupt the repository
$ . "$TESTDIR/histedit-helpers.sh"
$ cat >> $HGRCPATH <<EOF
> [extensions]
> histedit=
> EOF
$ initrepo ()
> {
> dir="$1"
> comment="$2"
> if [ -n "${comment}" ]; then
> echo % ${comment}
> echo % ${comment} | sed 's:.:-:g'
> fi
> hg init ${dir}
> cd ${dir}
> for x in a b c d e f ; do
> echo $x > $x
> hg add $x
> hg ci -m $x
> done
> cd ..
> }
$ geneditor ()
> {
> # generate an editor script for selecting changesets to be edited
> choice=$1 # changesets that should be edited (using sed line ranges)
> cat <<EOF | sed 's:^....::'
> # editing the rules, replacing 'pick' with 'edit' for the chosen lines
> sed '${choice}s:^pick:edit:' "\$1" > "\${1}.tmp"
> mv "\${1}.tmp" "\$1"
> # displaying the resulting rules, minus comments and empty lines
> sed '/^#/d;/^$/d;s:^:| :' "\$1" >&2
> EOF
> }
$ startediting ()
> {
> # begin an editing session
> choice="$1" # changesets that should be edited
> number="$2" # number of changesets considered (from tip)
> comment="$3"
> geneditor "${choice}" > edit.sh
> echo % start editing the history ${comment}
> HGEDITOR="sh ./edit.sh" hg histedit -- -${number} 2>&1 | fixbundle
> }
$ continueediting ()
> {
> # continue an edit already in progress
> editor="$1" # message editor when finalizing editing
> comment="$2"
> echo % finalize changeset editing ${comment}
> HGEDITOR=${editor} hg histedit --continue 2>&1 | fixbundle
> }
$ graphlog ()
> {
> comment="${1:-log}"
> echo % "${comment}"
> hg log -G --template '{rev} {node} \"{desc|firstline}\"\n'
> }
$ initrepo r1 "test editing with no change"
% test editing with no change
-----------------------------
$ cd r1
$ graphlog "log before editing"
% log before editing
@ 5 652413bf663ef2a641cab26574e46d5f5a64a55a "f"
|
o 4 e860deea161a2f77de56603b340ebbb4536308ae "e"
|
o 3 055a42cdd88768532f9cf79daa407fc8d138de9b "d"
|
o 2 177f92b773850b59254aa5e923436f921b55483b "c"
|
o 1 d2ae7f538514cd87c17547b0de4cea71fe1af9fb "b"
|
o 0 cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b "a"
$ startediting 2 3 "(not changing anything)" # edit the 2nd of 3 changesets
% start editing the history (not changing anything)
| pick 055a42cdd887 3 d
| edit e860deea161a 4 e
| pick 652413bf663e 5 f
0 files updated, 0 files merged, 2 files removed, 0 files unresolved
Editing (e860deea161a), commit as needed now to split the change
(to edit e860deea161a, `hg histedit --continue` after making changes)
$ continueediting true "(leaving commit message unaltered)"
% finalize changeset editing (leaving commit message unaltered)
check state of working copy
$ hg id
794fe033d0a0 tip
$ graphlog "log after history editing"
% log after history editing
@ 5 794fe033d0a030f8df77c5de945fca35c9181c30 "f"
|
o 4 04d2fab980779f332dec458cc944f28de8b43435 "e"
|
o 3 055a42cdd88768532f9cf79daa407fc8d138de9b "d"
|
o 2 177f92b773850b59254aa5e923436f921b55483b "c"
|
o 1 d2ae7f538514cd87c17547b0de4cea71fe1af9fb "b"
|
o 0 cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b "a"
$ cd ..
$ initrepo r2 "test editing with no change, then abort"
% test editing with no change, then abort
-----------------------------------------
$ cd r2
$ graphlog "log before editing"
% log before editing
@ 5 652413bf663ef2a641cab26574e46d5f5a64a55a "f"
|
o 4 e860deea161a2f77de56603b340ebbb4536308ae "e"
|
o 3 055a42cdd88768532f9cf79daa407fc8d138de9b "d"
|
o 2 177f92b773850b59254aa5e923436f921b55483b "c"
|
o 1 d2ae7f538514cd87c17547b0de4cea71fe1af9fb "b"
|
o 0 cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b "a"
$ startediting 1,2 3 "(not changing anything)" # edit the 1st two of 3 changesets
% start editing the history (not changing anything)
| edit 055a42cdd887 3 d
| edit e860deea161a 4 e
| pick 652413bf663e 5 f
0 files updated, 0 files merged, 3 files removed, 0 files unresolved
Editing (055a42cdd887), commit as needed now to split the change
(to edit 055a42cdd887, `hg histedit --continue` after making changes)
$ continueediting true "(leaving commit message unaltered)"
% finalize changeset editing (leaving commit message unaltered)
Editing (e860deea161a), commit as needed now to split the change
(to edit e860deea161a, `hg histedit --continue` after making changes)
$ graphlog "log after first edit"
% log after first edit
@ 6 e5ae3ca2f1ffdbd89ec41ebc273a231f7c3022f2 "d"
|
| o 5 652413bf663ef2a641cab26574e46d5f5a64a55a "f"
| |
| o 4 e860deea161a2f77de56603b340ebbb4536308ae "e"
| |
| o 3 055a42cdd88768532f9cf79daa407fc8d138de9b "d"
|/
o 2 177f92b773850b59254aa5e923436f921b55483b "c"
|
o 1 d2ae7f538514cd87c17547b0de4cea71fe1af9fb "b"
|
o 0 cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b "a"
abort editing session, after first forcibly updating away
$ hg up 0
abort: histedit in progress
(use 'hg histedit --continue' or 'hg histedit --abort')
[20]
$ mv .hg/histedit-state .hg/histedit-state-ignore
$ hg up 0
0 files updated, 0 files merged, 3 files removed, 0 files unresolved
$ mv .hg/histedit-state-ignore .hg/histedit-state
$ hg sum
parent: 0:cb9a9f314b8b
a
branch: default
commit: 1 added, 1 unknown (new branch head)
update: 6 new changesets (update)
phases: 7 draft
hist: 2 remaining (histedit --continue)
$ hg histedit --abort 2>&1 | fixbundle
modified files should survive the abort when we've moved away already
$ hg st
A e
? edit.sh
$ graphlog "log after abort"
% log after abort
o 5 652413bf663ef2a641cab26574e46d5f5a64a55a "f"
|
o 4 e860deea161a2f77de56603b340ebbb4536308ae "e"
|
o 3 055a42cdd88768532f9cf79daa407fc8d138de9b "d"
|
o 2 177f92b773850b59254aa5e923436f921b55483b "c"
|
o 1 d2ae7f538514cd87c17547b0de4cea71fe1af9fb "b"
|
@ 0 cb9a9f314b8b07ba71012fcdbc544b5a4d82ff5b "a"
aborting and not changing files can skip mentioning updating (no) files
$ hg up
5 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg commit --close-branch -m 'closebranch'
$ startediting 1 1 "(not changing anything)" # edit the 3rd of 3 changesets
% start editing the history (not changing anything)
| edit 292aec348d9e 6 closebranch
Editing (292aec348d9e), commit as needed now to split the change
(to edit 292aec348d9e, `hg histedit --continue` after making changes)
$ hg histedit --abort
$ cd ..