dir: update stale description of treat_directory()

The documentation comment for treat_directory() was originally written
in 095952 (Teach directory traversal about subprojects, 2007-04-11)
which was before the 'struct dir_struct' split its bitfield of named
options into a 'flags' enum in 7c4c97c0 (Turn the flags in struct
dir_struct into a single variable, 2009-02-16). When those flags
changed, the comment became stale, since members like
'show_other_directories' transitioned into flags like
DIR_SHOW_OTHER_DIRECTORIES.

Update the comments for treat_directory() to use these flag names rather
than the old member names.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

dir.c

@@ -1740,13 +1740,13 @@ static enum exist_status directory_exists_in_index(struct index_state *istate,
  * Case 3: if we didn't have it in the index previously, we
  * have a few sub-cases:
  *
- *  (a) if "show_other_directories" is true, we show it as
+ *  (a) if DIR_SHOW_OTHER_DIRECTORIES flag is set, we show it as
- *      just a directory, unless "hide_empty_directories" is
+ *      just a directory, unless DIR_HIDE_EMPTY_DIRECTORIES is
  *      also true, in which case we need to check if it contains any
  *      untracked and / or ignored files.
- *  (b) if it looks like a git directory, and we don't have
+ *  (b) if it looks like a git directory and we don't have the
- *      'no_gitlinks' set we treat it as a gitlink, and show it
+ *      DIR_NO_GITLINKS flag, then we treat it as a gitlink, and
- *      as a directory.
+ *      show it as a directory.
  *  (c) otherwise, we recurse into it.
  */
 static enum path_treatment treat_directory(struct dir_struct *dir,
@@ -1834,7 +1834,6 @@ static enum path_treatment treat_directory(struct dir_struct *dir,
 		return path_recurse;
 	}
 
-	/* This is the "show_other_directories" case */
 	assert(dir->flags & DIR_SHOW_OTHER_DIRECTORIES);
 
 	/*
@@ -1849,7 +1848,7 @@ static enum path_treatment treat_directory(struct dir_struct *dir,
 	/* Special cases for where this directory is excluded/ignored */
 	if (excluded) {
 		/*
-		 * In the show_other_directories case, if we're not
+		 * If DIR_SHOW_OTHER_DIRECTORIES is set and we're not
 		 * hiding empty directories, there is no need to
 		 * recurse into an ignored directory.
 		 */