Use merge-recursive in git-checkout -m (branch switching)

This allows "git checkout -m <other-branch>" to notice renames and
carry local changes in the working tree forward.

Signed-off-by: Junio C Hamano <junkio@cox.net>

git-checkout.sh

@@ -201,8 +201,9 @@ else
     	git diff-files --name-only | git update-index --remove --stdin &&
 	work=`git write-tree` &&
 	git read-tree --reset -u $new &&
-	git read-tree -m -u --aggressive --exclude-per-directory=.gitignore $old $new $work ||
-	exit
+	eval GITHEAD_$new=${new_name:-${branch:-$new}} GITHEAD_$work=local &&
+	export GITHEAD_$new GITHEAD_$work &&
+	git merge-recursive $old -- $new $work || exit
 
 	if result=`git write-tree 2>/dev/null`
 	then

t/t7201-co.sh

@@ -14,15 +14,23 @@ fill () {
 	done
 }
 
+
 test_expect_success setup '
 
-	fill 1 2 3 4 5 >one &&
+	fill 1 2 3 4 5 6 7 8 >one &&
 	fill a b c d e >two &&
 	git add one two &&
 	git commit -m "Initial A one, A two" &&
 
-	git checkout -b side &&
-	fill 1 2 3 >one &&
+	git checkout -b renamer &&
+	rm -f one &&
+	fill 1 3 4 5 6 7 8 >uno &&
+	git add uno &&
+	fill a b c d e f >two &&
+	git commit -a -m "Renamer R one->uno, M two" &&
+
+	git checkout -b side master &&
+	fill 1 2 3 4 5 6 7 >one &&
 	fill A B C D E >three &&
 	rm -f two &&
 	git update-index --add --remove one two three &&
@@ -42,7 +50,7 @@ test_expect_success "checkout from non-existing branch" '
 
 test_expect_success "checkout with dirty tree without -m" '
 
-	fill 0 1 2 3 4 5 >one &&
+	fill 0 1 2 3 4 5 6 7 8 >one &&
 	if git checkout side
 	then
 		echo Not happy
@@ -58,12 +66,10 @@ test_expect_success "checkout -m with dirty tree" '
 	git checkout -f master &&
 	git clean &&
 
-	fill 0 1 2 3 4 5 >one &&
+	fill 0 1 2 3 4 5 6 7 8 >one &&
 	git checkout -m side &&
 
-	fill "  master" "* side" >expect.branch &&
-	git branch >current.branch &&
-	diff expect.branch current.branch &&
+	test "$(git symbolic-ref HEAD)" = "refs/heads/side" &&
 
 	fill "M	one" "A	three" "D	two" >expect.master &&
 	git diff --name-status master >current.master &&
@@ -78,4 +84,23 @@ test_expect_success "checkout -m with dirty tree" '
 	diff expect.index current.index
 '
 
+test_expect_success "checkout -m with dirty tree, renamed" '
+
+	git checkout -f master && git clean &&
+
+	fill 1 2 3 4 5 7 8 >one &&
+	if git checkout renamer
+	then
+		echo Not happy
+		false
+	else
+		echo "happy - failed correctly"
+	fi &&
+
+	git checkout -m renamer &&
+	fill 1 3 4 5 7 8 >expect &&
+	diff expect uno &&
+	! test -f one
+'
+
 test_done