On this wiki, editing `templates/gitbranch.mdwn` causes a really slow
refresh, orders of magnitude slower than a full rebuild: a large number of
pages depend on that template, or link to a page that embeds that template,
and so on.

I suspect that, as with my optimization pass for `album`'s benefit, the
costly thing is evaluating lots of pagespecs. I'm profiling it to see
whether the problem is there are any low-hanging fruit.

Easy to reproduce offline:

* comment out the `exclude` option in `docwiki.setup`
* `/usr/bin/perl -Iblib/lib ikiwiki.in -setup docwiki.setup -rebuild`
* `touch templates/gitbranch.mdwn`
* `/usr/bin/perl -Iblib/lib ikiwiki.in -setup docwiki.setup -refresh`

--[[smcv]]