revision: mark blobs needed for resolve-undo as reachable

The resolve-undo extension was added to the index in cfc5789a
(resolve-undo: record resolved conflicts in a new index extension
section, 2009-12-25).  This extension records the blob object names
and their modes of conflicted paths when the path gets resolved
(e.g. with "git add"), to allow "undoing" the resolution with
"checkout -m path".  These blob objects should be guarded from
garbage-collection while we have the resolve-undo information in the
index (otherwise unresolve operation may try to use a blob object
that has already been pruned away).

But the code called from mark_reachable_objects() for the index
forgets to do so.  Teach add_index_objects_to_pending() helper to
also add objects referred to by the resolve-undo extension.

Also make matching changes to "fsck", which has code that is fairly
similar to the reachability stuff, but have parallel implementations
for all these stuff, which may (or may not) someday want to be unified.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/revision.c b/revision.c
index 7d435f8048..cd78627b20 100644
--- a/revision.c
+++ b/revision.c
@@ -33,6 +33,7 @@
 #include "bloom.h"
 #include "json-writer.h"
 #include "list-objects-filter-options.h"
+#include "resolve-undo.h"
 
 volatile show_early_output_fn_t show_early_output;
 
@@ -1690,6 +1691,39 @@ static void add_cache_tree(struct cache_tree *it, struct rev_info *revs,
 
 }
 
+static void add_resolve_undo_to_pending(struct index_state *istate, struct rev_info *revs)
+{
+	struct string_list_item *item;
+	struct string_list *resolve_undo = istate->resolve_undo;
+
+	if (!resolve_undo)
+		return;
+
+	for_each_string_list_item(item, resolve_undo) {
+		const char *path = item->string;
+		struct resolve_undo_info *ru = item->util;
+		int i;
+
+		if (!ru)
+			continue;
+		for (i = 0; i < 3; i++) {
+			struct blob *blob;
+
+			if (!ru->mode[i] || !S_ISREG(ru->mode[i]))
+				continue;
+
+			blob = lookup_blob(revs->repo, &ru->oid[i]);
+			if (!blob) {
+				warning(_("resolve-undo records `%s` which is missing"),
+					oid_to_hex(&ru->oid[i]));
+				continue;
+			}
+			add_pending_object_with_path(revs, &blob->object, "",
+						     ru->mode[i], path);
+		}
+	}
+}
+
 static void do_add_index_objects_to_pending(struct rev_info *revs,
 					    struct index_state *istate,
 					    unsigned int flags)
@@ -1718,6 +1752,8 @@ static void do_add_index_objects_to_pending(struct rev_info *revs,
 		add_cache_tree(istate->cache_tree, revs, &path, flags);
 		strbuf_release(&path);
 	}
+
+	add_resolve_undo_to_pending(istate, revs);
 }
 
 void add_index_objects_to_pending(struct rev_info *revs, unsigned int flags)