git-mv: search more precisely for source directory in index

A move of a directory should find the entries in the index by
searching for the name _including_ the slash. Otherwise, the
directory can be shadowed by a file when it matches the prefix
and is lexicographically smaller, e.g. "ab.c" shadows "ab/".

Noticed by Sergey Vlasov.

[jc: added Sergey's original reproduction recipe as a test case
 at the end of t7001.]

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

builtin-mv.c

@@ -146,21 +146,24 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
 				&& lstat(dst, &st) == 0)
 			bad = "cannot move directory over file";
 		else if (src_is_dir) {
+			const char *src_w_slash = add_slash(src);
+			int len_w_slash = length + 1;
 			int first, last;
 
 			modes[i] = WORKING_DIRECTORY;
 
-			first = cache_name_pos(src, length);
+			first = cache_name_pos(src_w_slash, len_w_slash);
 			if (first >= 0)
-				die ("Huh? %s/ is in index?", src);
+				die ("Huh? %.*s is in index?",
+						len_w_slash, src_w_slash);
 
 			first = -1 - first;
 			for (last = first; last < active_nr; last++) {
 				const char *path = active_cache[last]->name;
-				if (strncmp(path, src, length)
-						|| path[length] != '/')
+				if (strncmp(path, src_w_slash, len_w_slash))
 					break;
 			}
+			free((char *)src_w_slash);
 
 			if (last - first < 1)
 				bad = "source directory is empty";

t/t7001-mv.sh

@@ -105,4 +105,17 @@ test_expect_success "Michael Cassar's test case" '
 	}
 '
 
+rm -fr papers partA path?
+
+test_expect_success "Sergey Vlasov's test case" '
+	rm -fr .git &&
+	git init-db &&
+	mkdir ab &&
+	date >ab.c &&
+	date >ab/d &&
+	git add ab.c ab &&
+	git commit -m 'initial' &&
+	git mv ab a
+'
+
 test_done