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+directory listing API
+=====================
+
+The directory listing API is used to enumerate paths in the work tree,
+optionally taking `.git/info/exclude` and `.gitignore` files per
+directory into account.
+
+Data structure
+--------------
+
+`struct dir_struct` structure is used to pass directory traversal
+options to the library and to record the paths discovered.  A single
+`struct dir_struct` is used regardless of whether or not the traversal
+recursively descends into subdirectories.
+
+The notable options are:
+
+`exclude_per_dir`::
+
+	The name of the file to be read in each directory for excluded
+	files (typically `.gitignore`).
+
+`flags`::
+
+	A bit-field of options:
+
+`DIR_SHOW_IGNORED`:::
+
+	Return just ignored files in `entries[]`, not untracked
+	files. This flag is mutually exclusive with
+	`DIR_SHOW_IGNORED_TOO`.
+
+`DIR_SHOW_IGNORED_TOO`:::
+
+	Similar to `DIR_SHOW_IGNORED`, but return ignored files in
+	`ignored[]` in addition to untracked files in
+	`entries[]`. This flag is mutually exclusive with
+	`DIR_SHOW_IGNORED`.
+
+`DIR_KEEP_UNTRACKED_CONTENTS`:::
+
+	Only has meaning if `DIR_SHOW_IGNORED_TOO` is also set; if this is set, the
+	untracked contents of untracked directories are also returned in
+	`entries[]`.
+
+`DIR_SHOW_IGNORED_TOO_MODE_MATCHING`:::
+
+	Only has meaning if `DIR_SHOW_IGNORED_TOO` is also set; if
+	this is set, returns ignored files and directories that match
+	an exclude pattern. If a directory matches an exclude pattern,
+	then the directory is returned and the contained paths are
+	not. A directory that does not match an exclude pattern will
+	not be returned even if all of its contents are ignored. In
+	this case, the contents are returned as individual entries.
++
+If this is set, files and directories that explicitly match an ignore
+pattern are reported. Implicitly ignored directories (directories that
+do not match an ignore pattern, but whose contents are all ignored)
+are not reported, instead all of the contents are reported.
+
+`DIR_COLLECT_IGNORED`:::
+
+	Special mode for git-add. Return ignored files in `ignored[]` and
+	untracked files in `entries[]`. Only returns ignored files that match
+	pathspec exactly (no wildcards). Does not recurse into ignored
+	directories.
+
+`DIR_SHOW_OTHER_DIRECTORIES`:::
+
+	Include a directory that is not tracked.
+
+`DIR_HIDE_EMPTY_DIRECTORIES`:::
+
+	Do not include a directory that is not tracked and is empty.
+
+`DIR_NO_GITLINKS`:::
+
+	If set, recurse into a directory that looks like a Git
+	directory.  Otherwise it is shown as a directory.
+
+The result of the enumeration is left in these fields:
+
+`entries[]`::
+
+	An array of `struct dir_entry`, each element of which describes
+	a path.
+
+`nr`::
+
+	The number of members in `entries[]` array.
+
+`alloc`::
+
+	Internal use; keeps track of allocation of `entries[]` array.
+
+`ignored[]`::
+
+	An array of `struct dir_entry`, used for ignored paths with the
+	`DIR_SHOW_IGNORED_TOO` and `DIR_COLLECT_IGNORED` flags.
+
+`ignored_nr`::
+
+	The number of members in `ignored[]` array.
+
+Calling sequence
+----------------
+
+Note: index may be looked at for .gitignore files that are CE_SKIP_WORKTREE
+marked. If you to exclude files, make sure you have loaded index first.
+
+* Prepare `struct dir_struct dir` and clear it with `memset(&dir, 0,
+  sizeof(dir))`.
+
+* To add single exclude pattern, call `add_exclude_list()` and then
+  `add_exclude()`.
+
+* To add patterns from a file (e.g. `.git/info/exclude`), call
+  `add_excludes_from_file()` , and/or set `dir.exclude_per_dir`.  A
+  short-hand function `setup_standard_excludes()` can be used to set
+  up the standard set of exclude settings.
+
+* Set options described in the Data Structure section above.
+
+* Call `read_directory()`.
+
+* Use `dir.entries[]`.
+
+* Call `clear_directory()` when none of the contained elements are no longer in use.
+
+(JC)