revlog: add a C implementation of `headrevsdiff`
Python implementation of `headrevsdiff` can be very slow in the worst
case compared with the `heads` computation it replaces, since the
latter is done in C.
Even the average case of this Python implementation is still
noticeable in the profiles.
This patch makes the computation much much faster by doing it in C.
#require serve
$ hg init test
$ cd test
$ cat > .hg/hgrc <<EOF
> [extensions]
> # this is only necessary to check that the mapping from
> # interhg to websub works
> interhg =
>
> [websub]
> issues = s|Issue(\d+)|<a href="http://bts.example.org/issue\1">Issue\1</a>|
> tickets = s|ticket(\d+)|<a href="http://ticket.example.org/issue\1">Ticket\1</a>|i
>
> [interhg]
> # check that we maintain some interhg backwards compatibility...
> # yes, 'x' is a weird delimiter...
> markbugs = sxbugx<i class="\x">bug</i>x
> problems = sxPROBLEMx<i class="\x">problem</i>xi
> EOF
$ touch foo
$ hg add foo
$ hg commit -d '1 0' -m 'Issue123: fixed the bug! Ticket456 and problem789 too'
$ hg serve -n test -p $HGPORT -d --pid-file=hg.pid -A access.log -E errors.log
$ cat hg.pid >> $DAEMON_PIDS
log
$ get-with-headers.py localhost:$HGPORT "rev/tip" | grep bts
<div class="description"><a href="http://bts.example.org/issue123">Issue123</a>: fixed the <i class="x">bug</i>! <a href="http://ticket.example.org/issue456">Ticket456</a> and <i class="x">problem</i>789 too</div>
errors
$ cat errors.log
$ cd ..