tests/test-race

commands: add more robust support for 'hg log -b' (issue2078)

Fixes issue2078 and adds tests to cover various 'hg log -b' uses.

This change adds a localrepo.lookupbranch(key, remote=None) function. This
will look up the branch of the revision with the given key. The algorithm
works like this:

    * If a remote repo is given and KEY is the name of a branch in that repo,
      return KEY.
    * If no remote repo is given and KEY is the name of a branch in the local
      repo object, return KEY.
    * Otherwise look up the revision with the identifier KEY in the local repo
      and return its branch.

This change also makes 'hg log -b' use this new functionality and adds a few
tests for it.

#!/bin/sh

mkdir t
cd t
hg init
echo a > a
hg add a
hg commit -m test

# do we ever miss a sub-second change?
for i in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20; do
    hg co -qC 0
    echo b > a
    hg st
done