[PATCH v2 3/4] mark_reachable_objects(): optionally collect broken symrefs

[Johannes Schindelin <johannes.schindelin@gmx.de>]

The behavior of `mark_reachable_objects()` without this patch is that
it warns if it encounters a broken symref. Sometimes the caller wants
to act upon broken symrefs, e.g. when garbage collecting in a repository
with a broken remote HEAD.

So let's introduce an optional parameter to collect broken symrefs. The
behavior of the function is unchanged if that parameter is `NULL`.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 builtin/prune.c  |  2 +-
 builtin/reflog.c |  2 +-
 reachable.c      | 25 +++++++++++++++++++------
 reachable.h      |  3 ++-
 4 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/builtin/prune.c b/builtin/prune.c
index 10b03d3..d6f664f 100644
--- a/builtin/prune.c
+++ b/builtin/prune.c
@@ -136,7 +136,7 @@ int cmd_prune(int argc, const char **argv, const char *prefix)
 	if (show_progress)
 		progress = start_progress_delay(_("Checking connectivity"), 0, 0, 2);
 
-	mark_reachable_objects(&revs, 1, expire, progress);
+	mark_reachable_objects(&revs, 1, expire, progress, NULL);
 	stop_progress(&progress);
 	for_each_loose_file_in_objdir(get_object_directory(), prune_object,
 				      prune_cruft, prune_subdir, NULL);
diff --git a/builtin/reflog.c b/builtin/reflog.c
index f96ca2a..cb8758a 100644
--- a/builtin/reflog.c
+++ b/builtin/reflog.c
@@ -583,7 +583,7 @@ static int cmd_reflog_expire(int argc, const char **argv, const char *prefix)
 		init_revisions(&cb.cmd.revs, prefix);
 		if (flags & EXPIRE_REFLOGS_VERBOSE)
 			printf("Marking reachable objects...");
-		mark_reachable_objects(&cb.cmd.revs, 0, 0, NULL);
+		mark_reachable_objects(&cb.cmd.revs, 0, 0, NULL, NULL);
 		if (flags & EXPIRE_REFLOGS_VERBOSE)
 			putchar('\n');
 	}
diff --git a/reachable.c b/reachable.c
index 64289f3..25c4932 100644
--- a/reachable.c
+++ b/reachable.c
@@ -15,6 +15,11 @@ struct connectivity_progress {
 	unsigned long count;
 };
 
+struct add_one_data {
+	struct rev_info *revs;
+	struct string_list *broken_symrefs;
+};
+
 static void update_progress(struct connectivity_progress *cp)
 {
 	cp->count++;
@@ -25,16 +30,19 @@ static void update_progress(struct connectivity_progress *cp)
 static int add_one_ref(const char *path, const struct object_id *oid,
 		       int flag, void *cb_data)
 {
-	struct rev_info *revs = (struct rev_info *)cb_data;
+	struct add_one_data *data = (struct add_one_data *)cb_data;
 	struct object *object;
 
 	if ((flag & REF_ISSYMREF) && (flag & REF_ISBROKEN)) {
-		warning("ref is broken: %s", path);
+		if (data->broken_symrefs)
+			string_list_append(data->broken_symrefs, path);
+		else
+			warning("ref is broken: %s", path);
 		return 0;
 	}
 
 	object = parse_object_or_die(oid->hash, path);
-	add_pending_object(revs, object, "");
+	add_pending_object(data->revs, object, "");
 
 	return 0;
 }
@@ -159,9 +167,11 @@ int add_unseen_recent_objects_to_traversal(struct rev_info *revs,
 
 void mark_reachable_objects(struct rev_info *revs, int mark_reflog,
 			    unsigned long mark_recent,
-			    struct progress *progress)
+			    struct progress *progress,
+			    struct string_list *broken_symrefs)
 {
 	struct connectivity_progress cp;
+	struct add_one_data data;
 
 	/*
 	 * Set up revision parsing, and mark us as being interested
@@ -174,11 +184,14 @@ void mark_reachable_objects(struct rev_info *revs, int mark_reflog,
 	/* Add all refs from the index file */
 	add_index_objects_to_pending(revs, 0);
 
+	data.revs = revs;
+	data.broken_symrefs = broken_symrefs;
+
 	/* Add all external refs */
-	for_each_ref(add_one_ref, revs);
+	for_each_ref(add_one_ref, &data);
 
 	/* detached HEAD is not included in the list above */
-	head_ref(add_one_ref, revs);
+	head_ref(add_one_ref, &data);
 
 	/* Add all reflog info */
 	if (mark_reflog)
diff --git a/reachable.h b/reachable.h
index d23efc3..06f1400 100644
--- a/reachable.h
+++ b/reachable.h
@@ -5,6 +5,7 @@ struct progress;
 extern int add_unseen_recent_objects_to_traversal(struct rev_info *revs,
 						  unsigned long timestamp);
 extern void mark_reachable_objects(struct rev_info *revs, int mark_reflog,
-				   unsigned long mark_recent, struct progress *);
+				   unsigned long mark_recent, struct progress *,
+				   struct string_list *broken_symrefs);
 
 #endif
-- 
2.5.3.windows.1.3.gc322723