dir: move doc to dir.h

Move the documentation from Documentation/technical/api-directory-listing.txt
to dir.h as it's easier for the developers to find the usage information
beside the code instead of looking for it in another doc file.

Also documentation/technical/api-directory-listing.txt is removed because
the information it has is now redundant and it'll be hard to keep it up to
date and synchronized with the documentation in the header files.

Signed-off-by: Heba Waly <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: HebaWaly

Documentation/technical/api-directory-listing.txt

@@ -2,8 +2,6 @@
  * This handles recursive filename detection with exclude
  * files, index knowledge etc..
  *
- * See Documentation/technical/api-directory-listing.txt
- *
  * Copyright (C) Linus Torvalds, 2005-2006
  *		 Junio Hamano, 2005-2006
  */

dir.c

@@ -1,11 +1,44 @@
 #ifndef DIR_H
 #define DIR_H
 
-/* See Documentation/technical/api-directory-listing.txt */
-
 #include "cache.h"
 #include "strbuf.h"
 
+/**
+ * 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.
+ */
+
+/**
+ * Calling sequence
+ * ----------------
+ *
+ * Note: The index may be checked for .gitignore files that are
+ * CE_SKIP_WORKTREE marked. If you want to exclude files, make sure you have
+ * loaded the index first.
+ *
+ * - Prepare `struct dir_struct dir` and clear it with `memset(&dir, 0,
+ * sizeof(dir))`.
+ *
+ * - To add single exclude pattern, call `add_pattern_list()` and then
+ *   `add_pattern()`.
+ *
+ * - To add patterns from a file (e.g. `.git/info/exclude`), call
+ *   `add_patterns_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.
+ *
+ */
+
 struct dir_entry {
 	unsigned int len;
 	char name[FLEX_ARRAY]; /* more */
@@ -144,25 +177,101 @@ struct untracked_cache {
 	unsigned int use_fsmonitor : 1;
 };
 
+/**
+ * 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.
+ */
 struct dir_struct {
-	int nr, alloc;
-	int ignored_nr, ignored_alloc;
+
+	/* The number of members in `entries[]` array. */
+	int nr;
+
+	/* Internal use; keeps track of allocation of `entries[]` array.*/
+	int alloc;
+
+	/* The number of members in `ignored[]` array. */
+	int ignored_nr;
+
+	int ignored_alloc;
+
+	/* bit-field of options */
 	enum {
+
+		/**
+		 * Return just ignored files in `entries[]`, not untracked files.
+		 * This flag is mutually exclusive with `DIR_SHOW_IGNORED_TOO`.
+		 */
 		DIR_SHOW_IGNORED = 1<<0,
+
+		/* Include a directory that is not tracked. */
 		DIR_SHOW_OTHER_DIRECTORIES = 1<<1,
+
+		/* Do not include a directory that is not tracked and is empty. */
 		DIR_HIDE_EMPTY_DIRECTORIES = 1<<2,
+
+		/**
+		 * If set, recurse into a directory that looks like a Git directory.
+		 * Otherwise it is shown as a directory.
+		 */
 		DIR_NO_GITLINKS = 1<<3,
+
+		/**
+		 * 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_COLLECT_IGNORED = 1<<4,
+
+		/**
+		 * 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_SHOW_IGNORED_TOO = 1<<5,
+
 		DIR_COLLECT_KILLED_ONLY = 1<<6,
+
+		/**
+		 * 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_KEEP_UNTRACKED_CONTENTS = 1<<7,
+
+		/**
+		 * 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_SHOW_IGNORED_TOO_MODE_MATCHING = 1<<8,
+
 		DIR_SKIP_NESTED_GIT = 1<<9
 	} flags;
+
+	/* An array of `struct dir_entry`, each element of which describes a path. */
 	struct dir_entry **entries;
+
+	/**
+	 * used for ignored paths with the `DIR_SHOW_IGNORED_TOO` and
+	 * `DIR_COLLECT_IGNORED` flags.
+	 */
 	struct dir_entry **ignored;
 
-	/* Exclude info */
+	/**
+	 * The name of the file to be read in each directory for excluded files
+	 * (typically `.gitignore`).
+	 */
 	const char *exclude_per_dir;
 
 	/*