Issue a warning if "-r ." is used with two working directory parents.
Rationale for not aborting instead:
The first parent is usually more important as it is the local branch
during a merge and commands like 'hg diff' and 'hg diff -r.' behave still
identically (except for the warning of course).
Added a test for log -r. with one and two parents.
#!/bin/sh
hg init
touch unknown
touch a
hg add a
hg ci -m "1" -d "1000000 0"
touch b
hg add b
hg ci -m "2" -d "1000000 0"
echo %% Should show unknown
hg status
hg revert -r 0 --all
echo %% Should show unknown and b removed
hg status
echo %% Should show a and unknown
ls