[PATCHv2 3/4] cache.h: document add_[file_]to_index

@@ -609,13 +609,24 @@ extern int remove_index_entry_at(struct index_state *, int pos);
 
 extern void remove_marked_cache_entries(struct index_state *istate);
 extern int remove_file_from_index(struct index_state *, const char *path);
-#define ADD_CACHE_VERBOSE 1
-#define ADD_CACHE_PRETEND 2
-#define ADD_CACHE_IGNORE_ERRORS	4
-#define ADD_CACHE_IGNORE_REMOVAL 8
-#define ADD_CACHE_INTENT 16
+
+#define ADD_CACHE_VERBOSE 1		/* verbose */
+#define ADD_CACHE_PRETEND 2 		/* dry run */
+#define ADD_CACHE_IGNORE_ERRORS 4	/* ignore errors */
+#define ADD_CACHE_IGNORE_REMOVAL 8	/* do not remove files from index */
+#define ADD_CACHE_INTENT 16		/* intend to add later; stage empty file */
+/*
+ * These two are used to add the contents of the file at path
+ * to the index, marking the working tree up-to-date by storing
+ * the cached stat info in the resulting cache entry.  A caller
+ * that has already run lstat(2) on the path can call
+ * add_to_index(), and all others can call add_file_to_index();
+ * the latter will do necessary lstat(2) internally before
+ * calling the former.
+ */
 extern int add_to_index(struct index_state *, const char *path, struct stat *, int flags);
 extern int add_file_to_index(struct index_state *, const char *path, int flags);
+
 extern struct cache_entry *make_cache_entry(unsigned int mode, const unsigned char *sha1, const char *path, int stage, unsigned int refresh_options);
 extern int chmod_index_entry(struct index_state *, struct cache_entry *ce, char flip);
 extern int ce_same_name(const struct cache_entry *a, const struct cache_entry *b);