changegroup: store old heads as a set
Previously, the "oldheads" variable was a list. On a repository at
Mozilla with 46,492 heads, profiling revealed that list membership
testing was dominating execution time of applying small changegroups.
This patch converts the list of old heads to a set. This makes
membership testing significantly faster. On the aforementioned
repository with 46,492 heads:
$ hg unbundle <file with 1 changeset>
before: 18.535s wall
after: 1.303s
Consumers of this variable only check for truthiness (`if oldheads`),
length (`len(oldheads)`), and (most importantly) item membership
(`h not in oldheads` - which occurs twice). So, the change to a set
should be safe and suitable for stable.
The practical effect of this change is that changegroup application
and related operations (like `hg push`) no longer exhibit an O(n^2)
CPU explosion as the number of heads grows.
#require test-repo
Enable obsolescence to avoid the warning issue when obsmarker are found
$ . "$TESTDIR/helpers-testrepo.sh"
Go back in the hg repo
$ cd $TESTDIR/..
$ for node in `hg log --rev 'not public() and ::. and not desc("# no-check-commit")' --template '{node|short}\n'`; do
> hg export $node | contrib/check-commit > ${TESTTMP}/check-commit.out
> if [ $? -ne 0 ]; then
> echo "Revision $node does not comply with rules"
> echo '------------------------------------------------------'
> cat ${TESTTMP}/check-commit.out
> echo
> fi
> done