[PATCH] Enable and fix support for base less merges.

Let the merge strategies handle the base less case if they are able to
do it. It also fixes git-resolve.sh to die if no common ancestors
exists, instead of doing the wrong thing. Furthermore, it contains a
small independent fix for git-merge.sh and a fix for a base less code
path in gitMergeCommon.py.

With this it's possible to use
    git merge -s recursive 'merge message' A B
to do a base less merge of A and B.

[jc: Thanks Fredrik for fixing the brown-paper-bag in git-merge.
 I fixed a small typo in git-merge-resolve fix; 'test' equality
 check is spelled with single equal sign -- C-style double equal
 sign is bashism.]

Signed-off-by: Fredrik Kuivinen <freku045@student.liu.se>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-merge-resolve.sh

@@ -31,6 +31,12 @@ case "$remotes" in
 	exit 2 ;;
 esac
 
+# Give up if this is a baseless merge.
+if test '' = "$bases"
+then
+	exit 2
+fi
+
 git-update-index --refresh 2>/dev/null
 git-read-tree -u -m $bases $head $remotes || exit 2
 echo "Trying simple merge."