git-mv: fix moving more than one source to a single destination

The code used as if return value from basename(3) were stable, but
often the function is implemented to return a pointer to a static
storage internal to it.

Because basename(3) is also allowed to modify its input parameter in
place, casting constness away from the strings we obtained from the
caller and giving them to basename is a no-no.

Reported, and initial fix and test supplied by David Rydh.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-mv.c

@@ -24,10 +24,13 @@ static const char **copy_pathspec(const char *prefix, const char **pathspec,
 	result[count] = NULL;
 	for (i = 0; i < count; i++) {
 		int length = strlen(result[i]);
-		if (length > 0 && is_dir_sep(result[i][length - 1]))
-			result[i] = xmemdupz(result[i], length - 1);
-		if (base_name)
-			result[i] = basename((char *)result[i]);
+		int to_copy = length;
+		while (to_copy > 0 && is_dir_sep(result[i][to_copy - 1]))
+			to_copy--;
+		if (to_copy != length || base_name) {
+			char *it = xmemdupz(result[i], to_copy);
+			result[i] = base_name ? strdup(basename(it)) : it;
+		}
 	}
 	return get_pathspec(prefix, result);
 }

t/t7001-mv.sh

@@ -189,6 +189,18 @@ test_expect_success 'absolute pathname outside should fail' '(
 
 )'
 
+test_expect_success 'git mv to move multiple sources into a directory' '
+	rm -fr .git && git init &&
+	mkdir dir other &&
+	>dir/a.txt &&
+	>dir/b.txt &&
+	git add dir/?.txt &&
+	git mv dir/a.txt dir/b.txt other &&
+	git ls-files >actual &&
+	{ echo other/a.txt; echo other/b.txt; } >expect &&
+	test_cmp expect actual
+'
+
 test_expect_success 'git mv should not change sha1 of moved cache entry' '
 
 	rm -fr .git &&