revset: improve head revset performance
Previously the head() revset would iterate over every item in the subset and
check if it was a head. Since the subset is often the entire repo, this was
slow on large repos. Now we iterate over each item in the head list and check if
it's in the subset, which results in much less work.
hg log -r 'head()' on a large repo:
Before: 0.95s
After: 0.28s
Mercurial
=========
Mercurial is a fast, easy to use, distributed revision control tool
for software developers.
Basic install:
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
Running without installing:
$ make local # build for inplace usage
$ ./hg --version # should show the latest version
See http://mercurial.selenic.com/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.