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
echo "[extensions]" >> $HGRCPATH
echo "patchbomb=" >> $HGRCPATH
hg init
echo a > a
hg commit -Ama -d '1 0'
hg email --date '1970-1-1 0:1' -n -f quux -t foo -c bar tip | \
sed -e 's/\(Message-Id:.*@\).*/\1/'
echo b > b
hg commit -Amb -d '2 0'
hg email --date '1970-1-1 0:2' -n -f quux -t foo -c bar -s test 0:tip | \
sed -e 's/\(Message-Id:.*@\|In-Reply-To:.*@\).*/\1/'