attr.c: clarify the logic to pop attr_stack

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

diff --git a/attr.c b/attr.c
index a6e6523d29dcf021c4866660183f8442f44b7ff6..2ce73651381c8ebfa6dfed6c2013b72059861b2b 100644 (file)
--- a/attr.c
+++ b/attr.c
@@ -567,7 +567,9 @@ static void prepare_attr_stack(const char *path, int dirlen)
 
        /*
         * Pop the ones from directories that are not the prefix of
-        * the path we are checking.
+        * the path we are checking. Break out of the loop when we see
+        * the root one (whose origin is an empty string "") or the builtin
+        * one (whose origin is NULL) without popping it.
         */
        while (attr_stack->origin) {
                int namelen = strlen(attr_stack->origin);
@@ -587,6 +589,13 @@ static void prepare_attr_stack(const char *path, int dirlen)
         * Read from parent directories and push them down
         */
        if (!is_bare_repository() || direction == GIT_ATTR_INDEX) {
+               /*
+                * bootstrap_attr_stack() should have added, and the
+                * above loop should have stopped before popping, the
+                * root element whose attr_stack->origin is set to an
+                * empty string.
+                */
+               assert(attr_stack->origin);
                while (1) {
                        char *cp;