dir.c: refactor is_path_excluded()

In a similar way to the previous commit, this extracts a new helper
function last_exclude_matching_path() which return the last
exclude_list element which matched, or NULL if no match was found.
is_path_excluded() becomes a wrapper around this, and just returns 0
or 1 depending on whether any matching exclude_list element was found.

This allows callers to find out _why_ a given path was excluded,
rather than just whether it was or not, paving the way for a new git
sub-command which allows users to test their exclude lists from the
command line.

Signed-off-by: Adam Spiers <git@adamspiers.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

dir.c

@@ -709,6 +709,7 @@ void path_exclude_check_init(struct path_exclude_check *check,
 			     struct dir_struct *dir)
 {
 	check->dir = dir;
+	check->exclude = NULL;
 	strbuf_init(&check->path, 256);
 }
 
@@ -718,18 +719,21 @@ void path_exclude_check_clear(struct path_exclude_check *check)
 }
 
 /*
- * Is this name excluded?  This is for a caller like show_files() that
+ * For each subdirectory in name, starting with the top-most, checks
- * do not honor directory hierarchy and iterate through paths that are
+ * to see if that subdirectory is excluded, and if so, returns the
- * possibly in an ignored directory.
+ * corresponding exclude structure.  Otherwise, checks whether name
+ * itself (which is presumably a file) is excluded.
  *
  * A path to a directory known to be excluded is left in check->path to
  * optimize for repeated checks for files in the same excluded directory.
  */
-int is_path_excluded(struct path_exclude_check *check,
+struct exclude *last_exclude_matching_path(struct path_exclude_check *check,
-		     const char *name, int namelen, int *dtype)
+					   const char *name, int namelen,
+					   int *dtype)
 {
 	int i;
 	struct strbuf *path = &check->path;
+	struct exclude *exclude;
 
 	/*
 	 * we allow the caller to pass namelen as an optimization; it
@@ -739,11 +743,17 @@ int is_path_excluded(struct path_exclude_check *check,
 	if (namelen < 0)
 		namelen = strlen(name);
 
+	/*
+	 * If path is non-empty, and name is equal to path or a
+	 * subdirectory of path, name should be excluded, because
+	 * it's inside a directory which is already known to be
+	 * excluded and was previously left in check->path.
+	 */
 	if (path->len &&
 	    path->len <= namelen &&
 	    !memcmp(name, path->buf, path->len) &&
 	    (!name[path->len] || name[path->len] == '/'))
-		return 1;
+		return check->exclude;
 
 	strbuf_setlen(path, 0);
 	for (i = 0; name[i]; i++) {
@@ -751,8 +761,12 @@ int is_path_excluded(struct path_exclude_check *check,
 
 		if (ch == '/') {
 			int dt = DT_DIR;
-			if (is_excluded(check->dir, path->buf, &dt))
+			exclude = last_exclude_matching(check->dir,
-				return 1;
+							path->buf, &dt);
+			if (exclude) {
+				check->exclude = exclude;
+				return exclude;
+			}
 		}
 		strbuf_addch(path, ch);
 	}
@@ -760,7 +774,22 @@ int is_path_excluded(struct path_exclude_check *check,
 	/* An entry in the index; cannot be a directory with subentries */
 	strbuf_setlen(path, 0);
 
-	return is_excluded(check->dir, name, dtype);
+	return last_exclude_matching(check->dir, name, dtype);
+}
+
+/*
+ * Is this name excluded?  This is for a caller like show_files() that
+ * do not honor directory hierarchy and iterate through paths that are
+ * possibly in an ignored directory.
+ */
+int is_path_excluded(struct path_exclude_check *check,
+		  const char *name, int namelen, int *dtype)
+{
+	struct exclude *exclude =
+		last_exclude_matching_path(check, name, namelen, dtype);
+	if (exclude)
+		return exclude->flags & EXC_FLAG_NEGATIVE ? 0 : 1;
+	return 0;
 }
 
 static struct dir_entry *dir_entry_new(const char *pathname, int len)

dir.h

@@ -119,10 +119,13 @@ extern int match_pathname(const char *, int,
  */
 struct path_exclude_check {
 	struct dir_struct *dir;
+	struct exclude *exclude;
 	struct strbuf path;
 };
 extern void path_exclude_check_init(struct path_exclude_check *, struct dir_struct *);
 extern void path_exclude_check_clear(struct path_exclude_check *);
+extern struct exclude *last_exclude_matching_path(struct path_exclude_check *, const char *,
+						  int namelen, int *dtype);
 extern int is_path_excluded(struct path_exclude_check *, const char *, int namelen, int *dtype);