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 a
cd a
echo bar > foo
hg add foo
hg ci -m 'add foo' -d '1000000 0'

echo foobar > foo
hg ci -m 'change foo' -d '1000001 0'

echo 'quiet:'
hg --quiet diff -r 0 -r 1
echo

echo 'normal:'
hg diff -r 0 -r 1
echo

echo 'verbose:'
hg --verbose diff -r 0 -r 1
echo

echo 'debug:'
hg --debug diff -r 0 -r 1
echo