tests/test-debugindexdot

commands: Add 'hg log --branch' and deprecate 'hg log --only-branch'

Switching to --branch makes log consistent with push/pull and make more sense
given the actual behavior of the option (you can specify -b multiple times to
include multiple branches).

This change also adds some tests for 'hg log -b'.

#!/bin/sh

# Just exercize debugindexdot
# Create a short file history including a merge.
hg init t
cd t
echo a > a
hg ci -qAm t1 -d '0 0'
echo a >> a
hg ci -m t2 -d '1 0'
hg up -qC 0
echo b >> a
hg ci -m t3 -d '2 0'
HGMERGE=true hg merge -q
hg ci -m merge -d '3 0'

hg debugindexdot .hg/store/data/a.i