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 rep; cd rep
touch empty-file
python -c 'for x in range(10000): print x' > large-file
hg addremove
hg commit -m A
rm large-file empty-file
python -c 'for x in range(10,10000): print x' > another-file
hg addremove -s50
hg commit -m B
echo % comparing two empty files caused ZeroDivisionError in the past
hg update -C 0
rm empty-file
touch another-empty-file
hg addremove -s50
cd ..
hg init rep2; cd rep2
python -c 'for x in range(10000): print x' > large-file
python -c 'for x in range(50): print x' > tiny-file
hg addremove
hg commit -m A
python -c 'for x in range(70): print x' > small-file
rm tiny-file
rm large-file
hg addremove -s50
hg commit -m B