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
Testing templating for histedit command
Setup
$ cat >> $HGRCPATH <<EOF
> [extensions]
> histedit=
> [experimental]
> evolution=createmarkers
> EOF
$ hg init repo
$ cd repo
$ for ch in a b c d; do echo foo > $ch; hg commit -Aqm "Added "$ch; done
$ hg log -G -T "{rev}:{node|short} {desc}"
@ 3:62615734edd5 Added d
|
o 2:28ad74487de9 Added c
|
o 1:29becc82797a Added b
|
o 0:18d04c59bb5d Added a
Getting the JSON output for nodechanges
$ hg histedit -Tjson --commands - 2>&1 <<EOF
> pick 28ad74487de9 Added c
> pick 62615734edd5 Added d
> pick 18d04c59bb5d Added a
> pick 29becc82797a Added b
> EOF
[
{
"nodechanges": {"18d04c59bb5d2d4090ad9a5b59bd6274adb63add": ["109f8ec895447f81b380ba8d4d8b66539ccdcb94"], "28ad74487de9599d00d81085be739c61fc340652": ["bff9e07c1807942b161dab768aa793b48e9a7f9d"], "29becc82797a4bc11ec8880b58eaecd2ab3e7760": ["f5dcf3b4db23f31f1aacf46c33d1393de303d26f"], "62615734edd52f06b6fb9c2beb429e4fe30d57b8": ["201423b441c84d9e6858daed653e0d22485c1cfa"]}
}
]
$ hg log -G -T "{rev}:{node|short} {desc}"
@ 7:f5dcf3b4db23 Added b
|
o 6:109f8ec89544 Added a
|
o 5:201423b441c8 Added d
|
o 4:bff9e07c1807 Added c
$ hg histedit -T "{nodechanges|json}" --commands - 2>&1 <<EOF
> pick bff9e07c1807 Added c
> pick 201423b441c8 Added d
> pick 109f8ec89544 Added a
> roll f5dcf3b4db23 Added b
> EOF
{"109f8ec895447f81b380ba8d4d8b66539ccdcb94": ["8d01470bfeab64d3de13c49adb79d88790d38396"], "f3ec56a374bdbdf1953cacca505161442c6f3a3e": [], "f5dcf3b4db23f31f1aacf46c33d1393de303d26f": ["8d01470bfeab64d3de13c49adb79d88790d38396"]} (no-eol)