Many thanks to Josh Triplett for help with theses fixes:
1. Simplify the usage of git to eliminate the fragile and nasty
stuff we were doing previously, (such as manually symlinking
things under .git rather than just using git-clone -s).
2. Don't try running latest cairo-perf with LD_LIBRARY_PATH
pointing to built cairo version. Apparently stupid libtool
and its use of rpath is foiling us here. Instead just run
whatever cairo-perf gets built as part of the source that
gets checked out.
This second point means that cairo-perf-diff won't yet be useful
for comparing the performance of old cairo revisions that pre-date
cairo-perf. I've since been reasing and we might be able to use
--disable-rpath to the configure script to get what we want.
The old cairo-perf-diff is now named cairo-perf-diff-files, but
the new one calls out to it and can still be used in an identical
way.
The new cairo-perf-diff can also be used to see what the performance
impact of a single commit is like so:
cairo-perf-diff HEAD
or between two commits:
cairo-perf-diff 1.2.4 HEAD
The script is careful to always run the latest cairo-perf program
even when testing old versions of the library. Also, the output
from any given performance run is cached so it gets less painful
to run as the cache gets primed (the cache is in .perf next to
.git).
The script is still a bit fragile in spots. In particular it depends
on cairo-perf being built in advance but doesn't do anythin to ensure
that happens.
