Merge branch 'mh/mmap-packed-refs'

Operations that do not touch (majority of) packed refs have been
optimized by making accesses to packed-refs file lazy; we no longer
pre-parse everything, and an access to a single ref in the
packed-refs does not touch majority of irrelevant refs, either.

* mh/mmap-packed-refs: (21 commits)
  packed-backend.c: rename a bunch of things and update comments
  mmapped_ref_iterator: inline into `packed_ref_iterator`
  ref_cache: remove support for storing peeled values
  packed_ref_store: get rid of the `ref_cache` entirely
  ref_store: implement `refs_peel_ref()` generically
  packed_read_raw_ref(): read the reference from the mmapped buffer
  packed_ref_iterator_begin(): iterate using `mmapped_ref_iterator`
  read_packed_refs(): ensure that references are ordered when read
  packed_ref_cache: keep the `packed-refs` file mmapped if possible
  packed-backend.c: reorder some definitions
  mmapped_ref_iterator_advance(): no peeled value for broken refs
  mmapped_ref_iterator: add iterator over a packed-refs file
  packed_ref_cache: remember the file-wide peeling state
  read_packed_refs(): read references with minimal copying
  read_packed_refs(): make parsing of the header line more robust
  read_packed_refs(): only check for a header at the top of the file
  read_packed_refs(): use mmap to read the `packed-refs` file
  die_unterminated_line(), die_invalid_line(): new functions
  packed_ref_cache: add a backlink to the associated `packed_ref_store`
  prefix_ref_iterator: break when we leave the prefix
  ...

1 files changed, 21 insertions, 1 deletions

diff --git a/refs.c b/refs.c
index 6cfd88ff6b..df075fcd06 100644
--- a/refs.c
+++ b/refs.c
@@ -1285,6 +1285,10 @@ struct ref_iterator *refs_ref_iterator_begin(
 	if (trim)
 		iter = prefix_ref_iterator_begin(iter, "", trim);
 
+	/* Sanity check for subclasses: */
+	if (!iter->ordered)
+		BUG("reference iterator is not ordered");
+
 	return iter;
 }
 
@@ -1686,7 +1690,23 @@ int refs_pack_refs(struct ref_store *refs, unsigned int flags)
 int refs_peel_ref(struct ref_store *refs, const char *refname,
 		  unsigned char *sha1)
 {
-	return refs->be->peel_ref(refs, refname, sha1);
+	int flag;
+	unsigned char base[20];
+
+	if (current_ref_iter && current_ref_iter->refname == refname) {
+		struct object_id peeled;
+
+		if (ref_iterator_peel(current_ref_iter, &peeled))
+			return -1;
+		hashcpy(sha1, peeled.hash);
+		return 0;
+	}
+
+	if (refs_read_ref_full(refs, refname,
+			       RESOLVE_REF_READING, base, &flag))
+		return -1;
+
+	return peel_object(base, sha1);
 }
 
 int peel_ref(const char *refname, unsigned char *sha1)