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
Create a repository:
#if no-extraextensions
$ hg config
chgserver.idletimeout=60
devel.all-warnings=true
devel.default-date=0 0
extensions.fsmonitor= (fsmonitor !)
format.use-dirstate-v2=1 (dirstate-v2 !)
largefiles.usercache=$TESTTMP/.cache/largefiles
lfs.usercache=$TESTTMP/.cache/lfs
ui.slash=True
ui.interactive=False
ui.detailed-exit-code=True
ui.merge=internal:merge
ui.mergemarkers=detailed
ui.promptecho=True
ui.ssh=* (glob)
ui.timeout.warn=15
web.address=localhost
web\.ipv6=(?:True|False) (re)
web.server-header=testing stub value
#endif
$ hg init t
$ cd t
Prepare a changeset:
$ echo a > a
$ hg add a
$ hg status
A a
Writes to stdio succeed and fail appropriately
#if devfull
$ hg status 2>/dev/full
A a
$ hg status >/dev/full
abort: No space left on device* (glob)
[255]
#endif
#if devfull
$ hg status >/dev/full 2>&1
[255]
$ hg status ENOENT 2>/dev/full
[255]
#endif
On Python 3, stdio may be None:
$ hg debuguiprompt --config ui.interactive=true 0<&-
abort: Bad file descriptor (no-rhg !)
abort: response expected (rhg !)
[255]
$ hg version -q 0<&-
Mercurial Distributed SCM * (glob)
#if py3 no-rhg
$ hg version -q 1>&-
abort: Bad file descriptor
[255]
#else
$ hg version -q 1>&-
#endif
$ hg unknown -q 1>&-
hg: unknown command 'unknown'
(did you mean debugknown?)
[10]
$ hg version -q 2>&-
Mercurial Distributed SCM * (glob)
$ hg unknown -q 2>&-
[10]
$ hg commit -m test
This command is ancient:
$ hg history
changeset: 0:acb14030fe0a
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: test
Verify that updating to revision 0 via commands.update() works properly
$ cat <<EOF > update_to_rev0.py
> from mercurial import commands, hg, ui as uimod
> myui = uimod.ui.load()
> repo = hg.repository(myui, path=b'.')
> commands.update(myui, repo, rev=b"0")
> EOF
$ hg up null
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ "$PYTHON" ./update_to_rev0.py
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg identify -n
0
Poke around at hashes:
$ hg manifest --debug
b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3 644 a
$ hg cat a
a
Verify should succeed:
$ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
checked 1 changesets with 1 changes to 1 files
Repository root:
$ hg root
$TESTTMP/t
$ hg log -l1 -T '{reporoot}\n'
$TESTTMP/t
$ hg root -Tjson | sed 's|\\\\|\\|g'
[
{
"hgpath": "$TESTTMP/t/.hg",
"reporoot": "$TESTTMP/t",
"storepath": "$TESTTMP/t/.hg/store"
}
]
At the end...
$ cd ..
Status message redirection:
$ hg init empty
status messages are sent to stdout by default:
$ hg outgoing -R t empty -Tjson 2>/dev/null
comparing with empty
searching for changes
[
{
"bookmarks": [],
"branch": "default",
"date": [0, 0],
"desc": "test",
"node": "acb14030fe0a21b60322c440ad2d20cf7685a376",
"parents": ["0000000000000000000000000000000000000000"],
"phase": "draft",
"rev": 0,
"tags": ["tip"],
"user": "test"
}
]
which can be configured to send to stderr, so the output wouldn't be
interleaved:
$ cat <<'EOF' >> "$HGRCPATH"
> [ui]
> message-output = stderr
> EOF
$ hg outgoing -R t empty -Tjson 2>/dev/null
[
{
"bookmarks": [],
"branch": "default",
"date": [0, 0],
"desc": "test",
"node": "acb14030fe0a21b60322c440ad2d20cf7685a376",
"parents": ["0000000000000000000000000000000000000000"],
"phase": "draft",
"rev": 0,
"tags": ["tip"],
"user": "test"
}
]
$ hg outgoing -R t empty -Tjson >/dev/null
comparing with empty
searching for changes
this option should be turned off by HGPLAIN= since it may break scripting use:
$ HGPLAIN= hg outgoing -R t empty -Tjson 2>/dev/null
comparing with empty
searching for changes
[
{
"bookmarks": [],
"branch": "default",
"date": [0, 0],
"desc": "test",
"node": "acb14030fe0a21b60322c440ad2d20cf7685a376",
"parents": ["0000000000000000000000000000000000000000"],
"phase": "draft",
"rev": 0,
"tags": ["tip"],
"user": "test"
}
]
but still overridden by --config:
$ HGPLAIN= hg outgoing -R t empty -Tjson --config ui.message-output=stderr \
> 2>/dev/null
[
{
"bookmarks": [],
"branch": "default",
"date": [0, 0],
"desc": "test",
"node": "acb14030fe0a21b60322c440ad2d20cf7685a376",
"parents": ["0000000000000000000000000000000000000000"],
"phase": "draft",
"rev": 0,
"tags": ["tip"],
"user": "test"
}
]
Invalid ui.message-output option:
$ hg log -R t --config ui.message-output=bad
abort: invalid ui.message-output destination: bad
[255]
Underlying message streams should be updated when ui.fout/ferr are set:
$ cat <<'EOF' > capui.py
> import io
> from mercurial import registrar
> cmdtable = {}
> command = registrar.command(cmdtable)
> @command(b'capui', norepo=True)
> def capui(ui):
> out = ui.fout
> ui.fout = io.BytesIO()
> ui.status(b'status\n')
> ui.ferr = io.BytesIO()
> ui.warn(b'warn\n')
> out.write(b'stdout: %s' % ui.fout.getvalue())
> out.write(b'stderr: %s' % ui.ferr.getvalue())
> EOF
$ hg --config extensions.capui=capui.py --config ui.message-output=stdio capui
stdout: status
stderr: warn