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
== New Features ==
* New config `commands.commit.post-status` shows status after successful
commit.
* `hg root` now has templating support, including support for showing
where a repo share's source is. See `hg help -v root` for details.
* New `--force-close-branch` flag for `hg commit` to forcibly close
branch from a non-head changeset.
* The curses-based interface for commands like `hg commit -i` now supports
a range-select mechanism. Select the first line using space like before,
navigate to the last line, and press X (capital x) to set all items in
the range at once. Lowercase x has been added as a synonym for space to
help reinforce the mechanism, and pressing enter/return continues to be a
synonym for "toggle the current line and move down to the next item in
this section."
== New Experimental Features ==
* New config `experimental.log.topo` makes `hg log -G` use
topological sorting. This is especially useful for aliases since it
lets the alias accept an `-r` option while still using topological
sorting with or without the `-r` (unlike if you use the `sort(...,
topo)` revset).
== Bug Fixes ==
* issue4292: "hg log and {files} {file_adds} {file_mods} {file_dels}
in template show wrong files on merged revision". See details in
"Backwards Compatibility Changes".
== Backwards Compatibility Changes ==
* Removed (experimental) support for log graph lines mixing
parent/grandparent styles. Setting
e.g. `experimental.graphstyle.parent = !` and
`experimental.graphstyle.grandparent = 3.` would use `!` for the
first three lines of the graph and then `.`. This is no longer
supported.
* If `ui.origbackuppath` had been (incorrectly) configured to point
to a file, we will now replace that file by a directory and put
backups in that directory. This is similar to how we would
previously replace files *in* the configured directory by
subdirectories.
* Template keyword `{file_mods}`, `{file_adds}`, and `{file_dels}`
have changed behavior on merge commits. They used to be relative to
the first parent, but they now consider both parents. `{file_adds}`
shows files that exists in the commit but did not exist in either
parent. `{file_dels}` shows files that do not exist in the commit
but existed in either parent. `{file_mods}` show the remaining
files from `{files}` that were not in the other two
sets.
== Internal API Changes ==
* Matchers are no longer iterable. Use `match.files()` instead.
* `match.visitdir()` and `match.visitchildrenset()` now expect the
empty string instead of '.' to indicate the root directory.
* `util.dirs()` and `util.finddirs()` now include an entry for the
root directory (empty string).
* shelve is no longer an extension now. it will be turned on by default.
* New API to manage unfinished operations: Earlier there were distinct APIs
which dealt with unfinished states and separate lists maintaining them
that are `cmdutil.afterresolvestates`, `cmdutil.unfinishedstates` and
`cmdutil.STATES`. Now these have been unified to a single
API which handles the various states and their utilities. This API
has been added to `state.py`. Now instead of adding to these 3 lists
independently a state for a new operation can be registered using
`addunfinished()` in `state` module.
* `cmdutil.checkunfinished()` now includes detection for merge too.
* merge abort has been disallowed in case an operation of higher
precedence is in progress to avoid cases of partial abort of
operations.
* We used to automatically attempt to make extensions compatible with
Python 3 (by translating their source code while loading it). We no
longer do that.