changelog: add a `branch` method, bypassing changectx
The only way to access the branch of a changeset is currently to
create a changectx object and access its `branch()` method. Creating
a new Python object is costly and has a huge impact on code doing
heavy access to `branch()` (like branchmap).
This change introduces a new method on changelog that allows direct
access to the branch of a revision. See the next changeset for impact.
$ hg init
$ echo a > a
$ hg ci -qAm 'add a'
$ hg init subrepo
$ echo 'subrepo = http://example.net/libfoo' > .hgsub
$ hg ci -qAm 'added subrepo'
$ hg up -qC 0
$ echo ax > a
$ hg ci -m 'changed a'
created new head
$ hg up -qC 1
$ cd subrepo
$ echo b > b
$ hg add b
$ cd ..
Should fail, since there are added files to subrepo:
$ hg merge
abort: outstanding uncommitted changes in subrepository 'subrepo'
[255]