builtin-mv: minimum fix to avoid losing files

An incorrect command "git mv subdir /outer/space" threw the
subdirectory to outside of the repository and then noticed that
/outer/space/subdir/ would be outside of the repository.  The
error checking is backwards.

This fixes the issue by being careful about use of the return
value of get_pathspec().  Since the implementation already has
handcrafted loop to munge each path on the command line, we use
prefix_path() instead.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin-mv.c

@@ -19,6 +19,7 @@ static const char **copy_pathspec(const char *prefix, const char **pathspec,
 				  int count, int base_name)
 {
 	int i;
+	int len = prefix ? strlen(prefix) : 0;
 	const char **result = xmalloc((count + 1) * sizeof(const char *));
 	memcpy(result, pathspec, count * sizeof(const char *));
 	result[count] = NULL;
@@ -32,8 +33,11 @@ static const char **copy_pathspec(const char *prefix, const char **pathspec,
 			if (last_slash)
 				result[i] = last_slash + 1;
 		}
+		result[i] = prefix_path(prefix, len, result[i]);
+		if (!result[i])
+			exit(1); /* error already given */
 	}
-	return get_pathspec(prefix, result);
+	return result;
 }
 
 static void show_list(const char *label, struct path_list *list)

t/t7001-mv.sh

@@ -118,4 +118,42 @@ test_expect_success "Sergey Vlasov's test case" '
 	git mv ab a
 '
 
+test_expect_success 'absolute pathname' '(
+
+	rm -fr mine &&
+	mkdir mine &&
+	cd mine &&
+	test_create_repo one &&
+	cd one &&
+	mkdir sub &&
+	>sub/file &&
+	git add sub/file &&
+
+	git mv sub "$(pwd)/in" &&
+	! test -d sub &&
+	test -d in &&
+	git ls-files --error-unmatch in/file
+
+
+)'
+
+test_expect_success 'absolute pathname outside should fail' '(
+
+	rm -fr mine &&
+	mkdir mine &&
+	cd mine &&
+	out=$(pwd) &&
+	test_create_repo one &&
+	cd one &&
+	mkdir sub &&
+	>sub/file &&
+	git add sub/file &&
+
+	! git mv sub "$out/out" &&
+	test -d sub &&
+	! test -d ../in &&
+	git ls-files --error-unmatch sub/file
+
+)'
+
 test_done