branch: roll show_detached HEAD into regular ref_list

Remove show_detached() and make detached HEAD to be rolled into
regular ref_list by adding REF_DETACHED_HEAD as a kind of branch and
supporting the same in append_ref(). This eliminates the need for an
extra function and helps in easier porting of branch.c to use
ref-filter APIs.

Before show_detached() used to check if the HEAD branch satisfies the
'--contains' option, now that is taken care by append_ref().

Based-on-patch-by: Jeff King <peff@peff.net>
Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: Matthieu Moy <matthieu.moy@grenoble-inp.fr>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/branch.c

@@ -28,8 +28,9 @@ static const char * const builtin_branch_usage[] = {
 	NULL
 };
 
-#define REF_LOCAL_BRANCH    0x01
-#define REF_REMOTE_BRANCH   0x02
+#define REF_DETACHED_HEAD   0x01
+#define REF_LOCAL_BRANCH    0x02
+#define REF_REMOTE_BRANCH   0x04
 
 static const char *head;
 static unsigned char head_sha1[20];
@@ -352,8 +353,12 @@ static int append_ref(const char *refname, const struct object_id *oid, int flag
 			break;
 		}
 	}
-	if (ARRAY_SIZE(ref_kind) <= i)
-		return 0;
+	if (ARRAY_SIZE(ref_kind) <= i) {
+		if (!strcmp(refname, "HEAD"))
+			kind = REF_DETACHED_HEAD;
+		else
+			return 0;
+	}
 
 	/* Don't add types the caller doesn't want */
 	if ((kind & ref_list->kinds) == 0)
@@ -535,6 +540,8 @@ static void print_ref_item(struct ref_item *item, int maxwidth, int verbose,
 	int color;
 	struct strbuf out = STRBUF_INIT, name = STRBUF_INIT;
 	const char *prefix = "";
+	const char *desc = item->name;
+	char *to_free = NULL;
 
 	if (item->ignore)
 		return;
@@ -547,6 +554,10 @@ static void print_ref_item(struct ref_item *item, int maxwidth, int verbose,
 		color = BRANCH_COLOR_REMOTE;
 		prefix = remote_prefix;
 		break;
+	case REF_DETACHED_HEAD:
+		color = BRANCH_COLOR_CURRENT;
+		desc = to_free = get_head_description();
+		break;
 	default:
 		color = BRANCH_COLOR_PLAIN;
 		break;
@@ -558,7 +569,7 @@ static void print_ref_item(struct ref_item *item, int maxwidth, int verbose,
 		color = BRANCH_COLOR_CURRENT;
 	}
 
-	strbuf_addf(&name, "%s%s", prefix, item->name);
+	strbuf_addf(&name, "%s%s", prefix, desc);
 	if (verbose) {
 		int utf8_compensation = strlen(name.buf) - utf8_strwidth(name.buf);
 		strbuf_addf(&out, "%c %s%-*s%s", c, branch_get_color(color),
@@ -581,6 +592,7 @@ static void print_ref_item(struct ref_item *item, int maxwidth, int verbose,
 	}
 	strbuf_release(&name);
 	strbuf_release(&out);
+	free(to_free);
 }
 
 static int calc_maxwidth(struct ref_list *refs, int remote_bonus)
@@ -601,22 +613,6 @@ static int calc_maxwidth(struct ref_list *refs, int remote_bonus)
 	return max;
 }
 
-static void show_detached(struct ref_list *ref_list, int maxwidth)
-{
-	struct commit *head_commit = lookup_commit_reference_gently(head_sha1, 1);
-
-	if (head_commit && is_descendant_of(head_commit, ref_list->with_commit)) {
-		struct ref_item item;
-		item.name = get_head_description();
-		item.kind = REF_LOCAL_BRANCH;
-		item.dest = NULL;
-		item.commit = head_commit;
-		item.ignore = 0;
-		print_ref_item(&item, maxwidth, ref_list->verbose, ref_list->abbrev, 1, "");
-		free(item.name);
-	}
-}
-
 static int print_ref_list(int kinds, int detached, int verbose, int abbrev, struct commit_list *with_commit, const char **pattern)
 {
 	int i;
@@ -643,7 +639,14 @@ static int print_ref_list(int kinds, int detached, int verbose, int abbrev, stru
 	cb.ref_list = &ref_list;
 	cb.pattern = pattern;
 	cb.ret = 0;
+	/*
+	 * First we obtain all regular branch refs and if the HEAD is
+	 * detached then we insert that ref to the end of the ref_fist
+	 * so that it can be printed and removed first.
+	 */
 	for_each_rawref(append_ref, &cb);
+	if (detached)
+		head_ref(append_ref, &cb);
 	/*
 	 * The following implementation is currently duplicated in ref-filter. It
 	 * will eventually be removed when we port branch.c to use ref-filter APIs.
@@ -681,14 +684,12 @@ static int print_ref_list(int kinds, int detached, int verbose, int abbrev, stru
 
 	qsort(ref_list.list, ref_list.index, sizeof(struct ref_item), ref_cmp);
 
-	detached = (detached && (kinds & REF_LOCAL_BRANCH));
-	if (detached && match_patterns(pattern, "HEAD"))
-		show_detached(&ref_list, maxwidth);
-
 	for (i = 0; i < ref_list.index; i++) {
-		int current = !detached &&
-			(ref_list.list[i].kind == REF_LOCAL_BRANCH) &&
+		int current = !detached && (ref_list.list[i].kind == REF_LOCAL_BRANCH) &&
 			!strcmp(ref_list.list[i].name, head);
+		/*  If detached the first ref_item is the current ref */
+		if (detached && i == 0)
+			current = 1;
 		print_ref_item(&ref_list.list[i], maxwidth, verbose,
 			       abbrev, current, remote_prefix);
 	}
@@ -914,7 +915,11 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 			die(_("branch name required"));
 		return delete_branches(argc, argv, delete > 1, kinds, quiet);
 	} else if (list) {
-		int ret = print_ref_list(kinds, detached, verbose, abbrev,
+		int ret;
+		/*  git branch --local also shows HEAD when it is detached */
+		if (kinds & REF_LOCAL_BRANCH)
+			kinds |= REF_DETACHED_HEAD;
+		ret = print_ref_list(kinds, detached, verbose, abbrev,
 					 with_commit, argv);
 		print_columns(&output, colopts, NULL);
 		string_list_clear(&output, 0);