[PATCH] Fix bisection terminating condition

When testing bisection and using gitk to visualize the result, it was
obvious that the termination condition was broken.

We know what the bad entry is only when the bisection ends up telling us
to test the known-bad entry again.

Also, add a safety net: if somebody marks as good something that includes
the known-bad point, we now notice and complain, instead of writing an
empty revision to the new bisection branch.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-bisect-script

@@ -105,12 +105,16 @@ bisect_next() {
 	good=$(git-rev-parse --sq --revs-only --not \
 		$(cd "$GIT_DIR" && ls refs/bisect/good-*)) &&
 	rev=$(eval "git-rev-list --bisect $good $bad") || exit
-	nr=$(eval "git-rev-list $rev $good" | wc -l) || exit
-	if [ "$nr" -le "1" ]; then
+	if [ -z "$rev" ]; then
+	    echo "$bad was both good and bad"
+	    exit 1
+	fi
+	if [ "$rev" = "$bad" ]; then
 	    echo "$rev is first bad commit"
 	    git-diff-tree --pretty $rev
 	    exit 0
 	fi
+	nr=$(eval "git-rev-list $rev $good" | wc -l) || exit
 	echo "Bisecting: $nr revisions left to test after this"
 	echo "$rev" > "$GIT_DIR/refs/heads/new-bisect"
 	git checkout new-bisect || exit