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 cloning with the EOL extension
$ cat >> $HGRCPATH <<EOF
> [extensions]
> eol =
>
> [eol]
> native = CRLF
> EOF
setup repository
$ hg init repo
$ cd repo
$ cat > .hgeol <<EOF
> [patterns]
> **.txt = native
> EOF
$ printf "first\r\nsecond\r\nthird\r\n" > a.txt
$ hg commit --addremove -m 'checkin'
adding .hgeol
adding a.txt
Test commit of removed .hgeol and how it immediately makes the automatic
changes explicit and committable.
$ cd ..
$ hg clone repo repo-2
updating to branch default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd repo-2
$ cat a.txt
first\r (esc)
second\r (esc)
third\r (esc)
$ hg cat a.txt
first
second
third
$ hg remove .hgeol
$ touch a.txt * # ensure consistent st dirtyness checks, ignoring dirstate timing
$ hg st -v --debug
M a.txt
R .hgeol
$ hg commit -m 'remove eol'
$ hg exp
# HG changeset patch
# User test
# Date 0 0
# Thu Jan 01 00:00:00 1970 +0000
# Node ID 3c20c2d90333b6ecdc8f7aa8f9b73223c7c7a608
# Parent 90f94e2cf4e24628afddd641688dfe4cd476d6e4
remove eol
diff -r 90f94e2cf4e2 -r 3c20c2d90333 .hgeol
--- a/.hgeol Thu Jan 01 00:00:00 1970 +0000
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,2 +0,0 @@
-[patterns]
-**.txt = native
diff -r 90f94e2cf4e2 -r 3c20c2d90333 a.txt
--- a/a.txt Thu Jan 01 00:00:00 1970 +0000
+++ b/a.txt Thu Jan 01 00:00:00 1970 +0000
@@ -1,3 +1,3 @@
-first
-second
-third
+first\r (esc)
+second\r (esc)
+third\r (esc)
$ hg push --quiet
$ cd ..
Test clone of repo with .hgeol in working dir, but no .hgeol in default
checkout revision tip. The repo is correctly updated to be consistent and have
the exact content checked out without filtering, ignoring the current .hgeol in
the source repo:
$ cat repo/.hgeol
[patterns]
**.txt = native
$ hg clone repo repo-3 -v --debug
linked 7 files
updating to branch default
resolving manifests
branchmerge: False, force: False, partial: False
ancestor: 000000000000, local: 000000000000+, remote: 3c20c2d90333
calling hook preupdate.eol: hgext.eol.preupdate
a.txt: remote created -> g
getting a.txt
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
updating the branch cache
$ cd repo-3
$ cat a.txt
first\r (esc)
second\r (esc)
third\r (esc)
Test clone of revision with .hgeol
$ cd ..
$ hg clone -r 0 repo repo-4
adding changesets
adding manifests
adding file changes
added 1 changesets with 2 changes to 2 files
new changesets 90f94e2cf4e2
updating to branch default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd repo-4
$ cat .hgeol
[patterns]
**.txt = native
$ cat a.txt
first\r (esc)
second\r (esc)
third\r (esc)
$ cd ..