git-mv: succeed even if source is a prefix of destination

As noted by Fredrik Kuivinen, without this patch, git-mv fails on

	git-mv README README-renamed

because "README" is a prefix of "README-renamed".

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-mv.c

@@ -119,6 +119,7 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 
 	/* Checking */
 	for (i = 0; i < count; i++) {
+		int length;
 		const char *bad = NULL;
 
 		if (show_only)
@@ -204,7 +205,9 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 		}
 
 		if (!bad &&
-		    !strncmp(destination[i], source[i], strlen(source[i])))
+		    (length = strlen(source[i])) >= 0 &&
+		    !strncmp(destination[i], source[i], length) &&
+		    (destination[i][length] == 0 || destination[i][length] == '/'))
 			bad = "can not move directory into itself";
 
 		if (!bad && cache_name_pos(source[i], strlen(source[i])) < 0)

t/t7001-mv.sh

@@ -59,6 +59,10 @@ test_expect_success \
      git-diff-tree -r -M --name-status  HEAD^ HEAD | \
      grep -E "^R100.+path0/README.+path2/README"'
 
+test_expect_success \
+    'succeed when source is a prefix of destination' \
+    'git-mv path2/COPYING path2/COPYING-renamed'
+
 test_expect_success \
     'moving whole subdirectory into subdirectory' \
     'git-mv path2 path1'