Add searching for named branches
named branching is when you identify a head by a tag on an earlier revision.
This patch adds repo.branchlookup for searching through the tree to
find branch tags for heads.
hg update -b tag is added to checkout based on branch tags
hg heads -b is added to print the tag associated with each head
\.orig$
\.rej$
~$
\.so$
\.pyc$
\.swp$
\.prof$
^tests/.*\.err$
^build/
^dist/
^doc/.*\.[0-9](\.(x|ht)ml)?$
^MANIFEST$
^\.pc/
^patches/
^mercurial/__version__.py$