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 <<EOF >> $HGRCPATH
> [extensions]
> notify=
>
> [hooks]
> changegroup.notify = python:hgext.notify.hook
>
> [notify]
> sources = push
> diffstat = False
> maxsubject = 10
>
> [usersubs]
> foo@bar = *
>
> [reposubs]
> * = baz
> EOF
$ hg init a
clone
$ hg --traceback clone a b
updating to branch default
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo a > b/a
commit
$ hg --traceback --cwd b commit -Ama
adding a
$ echo a >> b/a
commit
$ hg --traceback --cwd b commit -Amb
push
$ hg --traceback --cwd b push ../a 2>&1 |
> "$PYTHON" $TESTDIR/unwrap-message-id.py | \
> "$PYTHON" -c 'import sys,re; print(re.sub("\n\t", " ", sys.stdin.read()), end="")'
pushing to ../a
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 1 files
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Date: * (glob)
Subject: * (glob)
From: test
X-Hg-Notification: changeset cb9a9f314b8b
Message-Id: <*> (glob)
To: baz, foo@bar
changeset cb9a9f314b8b in $TESTTMP/a
details: $TESTTMP/a?cmd=changeset;node=cb9a9f314b8b
summary: a
changeset ba677d0156c1 in $TESTTMP/a
details: $TESTTMP/a?cmd=changeset;node=ba677d0156c1
summary: b
diffs (6 lines):
diff -r 000000000000 -r ba677d0156c1 a
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/a Thu Jan 01 00:00:00 1970 +0000
@@ -0,0 +1,2 @@
+a
+a
$ hg --cwd a rollback
repository tip rolled back to revision -1 (undo push)
unbundle with unrelated source
$ hg --cwd b bundle ../test.hg ../a
searching for changes
2 changesets found
$ hg --cwd a unbundle ../test.hg
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 1 files
new changesets cb9a9f314b8b:ba677d0156c1 (2 drafts)
(run 'hg update' to get a working copy)
$ hg --cwd a rollback
repository tip rolled back to revision -1 (undo unbundle)
unbundle with correct source
$ hg --config notify.sources=unbundle --cwd a unbundle ../test.hg 2>&1 |
> "$PYTHON" $TESTDIR/unwrap-message-id.py | \
> "$PYTHON" -c 'import sys,re; print(re.sub("\n\t", " ", sys.stdin.read()), end="")'
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 1 files
new changesets cb9a9f314b8b:ba677d0156c1 (2 drafts)
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Date: * (glob)
Subject: * (glob)
From: test
X-Hg-Notification: changeset cb9a9f314b8b
Message-Id: <*> (glob)
To: baz, foo@bar
changeset cb9a9f314b8b in $TESTTMP/a
details: $TESTTMP/a?cmd=changeset;node=cb9a9f314b8b
summary: a
changeset ba677d0156c1 in $TESTTMP/a
details: $TESTTMP/a?cmd=changeset;node=ba677d0156c1
summary: b
diffs (6 lines):
diff -r 000000000000 -r ba677d0156c1 a
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/a Thu Jan 01 00:00:00 1970 +0000
@@ -0,0 +1,2 @@
+a
+a
(run 'hg update' to get a working copy)
Check that using the first committer as the author of a changeset works:
Check that the config option works.
Check that the first committer is indeed used for "From:".
Check that the merge user is NOT used for "From:"
Create new file
$ echo a > b/b
$ echo b >> b/b
$ echo c >> b/b
$ hg --traceback --cwd b commit -Amnewfile -u committer_1
adding b
commit as one user
$ echo x > b/b
$ echo b >> b/b
$ echo c >> b/b
$ hg --traceback --cwd b commit -Amx -u committer_2
commit as other user, change file so we can do an (automatic) merge
$ hg --cwd b up 2
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo a > b/b
$ echo b >> b/b
$ echo y >> b/b
$ hg --traceback --cwd b commit -Amy -u committer_3
created new head
merge as a different user
$ hg --cwd b merge --config notify.fromauthor=True
merging b
0 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg --traceback --cwd b commit -Am "merged"
push
$ hg --traceback --cwd b --config notify.fromauthor=True push ../a 2>&1 |
> "$PYTHON" $TESTDIR/unwrap-message-id.py | \
> "$PYTHON" -c 'import sys,re; print(re.sub("\n\t", " ", sys.stdin.read()), end="")'
pushing to ../a
searching for changes
adding changesets
adding manifests
adding file changes
added 4 changesets with 4 changes to 1 files
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Date: * (glob)
Subject: * (glob)
From: committer_1
X-Hg-Notification: changeset 84e487dddc58
Message-Id: <*> (glob)
To: baz, foo@bar
changeset 84e487dddc58 in $TESTTMP/a
details: $TESTTMP/a?cmd=changeset;node=84e487dddc58
summary: newfile
changeset b29c7a2b6b0c in $TESTTMP/a
details: $TESTTMP/a?cmd=changeset;node=b29c7a2b6b0c
summary: x
changeset 0957c7d64886 in $TESTTMP/a
details: $TESTTMP/a?cmd=changeset;node=0957c7d64886
summary: y
changeset 485b4e6b0249 in $TESTTMP/a
details: $TESTTMP/a?cmd=changeset;node=485b4e6b0249
summary: merged
diffs (7 lines):
diff -r ba677d0156c1 -r 485b4e6b0249 b
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/b Thu Jan 01 00:00:00 1970 +0000
@@ -0,0 +1,3 @@
+x
+b
+y
$ hg --cwd a rollback
repository tip rolled back to revision 1 (undo push)