refs: document flags constants REF_*

Document the bits that can appear in the "flags" parameter passed to
an each_ref_function and/or in the ref_entry::flag field.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs.c

@@ -157,7 +157,17 @@ struct ref_dir {
 	struct ref_entry **entries;
 };
 
-/* ISSYMREF=0x01, ISPACKED=0x02, and ISBROKEN=0x04 are public interfaces */
+/*
+ * Bit values for ref_entry::flag.  REF_ISSYMREF=0x01,
+ * REF_ISPACKED=0x02, and REF_ISBROKEN=0x04 are public values; see
+ * refs.h.
+ */
+
+/*
+ * The field ref_entry->u.value.peeled of this value entry contains
+ * the correct peeled value for the reference, which might be
+ * null_sha1 if the reference is not a tag or if it is broken.
+ */
 #define REF_KNOWS_PEELED 0x08
 
 /* ref_entry represents a directory of references */

refs.h

@@ -10,8 +10,21 @@ struct ref_lock {
 	int force_write;
 };
 
+/*
+ * Bit values set in the flags argument passed to each_ref_fn():
+ */
+
+/* Reference is a symbolic reference. */
 #define REF_ISSYMREF 0x01
+
+/* Reference is a packed reference. */
 #define REF_ISPACKED 0x02
+
+/*
+ * Reference cannot be resolved to an object name: dangling symbolic
+ * reference (directly or indirectly), corrupt reference file, or
+ * symbolic reference refers to ill-formatted reference name.
+ */
 #define REF_ISBROKEN 0x04
 
 /*