test-fetch: fix non-portable sed regex.
(s/...\+/.../ appears to be a GNU-ism: this test broke on OS X and
NetBSD. Changing \+ to * fixes it, although that is a slightly less
strict regex.)
branch heads: optimise computation of branch head cache (
issue1734)
The previous branch heads cache implementation iterated all ancestors
for each new revision in the repository, causing a massive slowdown on
cloning larger repositories.