Convert lookup_commit* to struct object_id

Convert lookup_commit, lookup_commit_or_die,
lookup_commit_reference, and lookup_commit_reference_gently to take
struct object_id arguments.

Introduce a temporary in parse_object buffer in order to convert this
function.  This is required since in order to convert parse_object and
parse_object_buffer, lookup_commit_reference_gently and
lookup_commit_or_die would need to be converted.  Not introducing a
temporary would therefore require that lookup_commit_or_die take a
struct object_id *, but lookup_commit would take unsigned char *,
leaving a confusing and hard-to-use interface.

parse_object_buffer will lose this temporary in a later patch.

This commit was created with manual changes to commit.c, commit.h, and
object.c, plus the following semantic patch:

@@
expression E1, E2;
@@
- lookup_commit_reference_gently(E1.hash, E2)
+ lookup_commit_reference_gently(&E1, E2)

@@
expression E1, E2;
@@
- lookup_commit_reference_gently(E1->hash, E2)
+ lookup_commit_reference_gently(E1, E2)

@@
expression E1;
@@
- lookup_commit_reference(E1.hash)
+ lookup_commit_reference(&E1)

@@
expression E1;
@@
- lookup_commit_reference(E1->hash)
+ lookup_commit_reference(E1)

@@
expression E1;
@@
- lookup_commit(E1.hash)
+ lookup_commit(&E1)

@@
expression E1;
@@
- lookup_commit(E1->hash)
+ lookup_commit(E1)

@@
expression E1, E2;
@@
- lookup_commit_or_die(E1.hash, E2)
+ lookup_commit_or_die(&E1, E2)

@@
expression E1, E2;
@@
- lookup_commit_or_die(E1->hash, E2)
+ lookup_commit_or_die(E1, E2)

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/notes-merge.c b/notes-merge.c
index 06d8be9..6244f6a 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -554,7 +554,7 @@ int notes_merge(struct notes_merge_options *o,
 	else if (!check_refname_format(o->local_ref, 0) &&
 		is_null_oid(&local_oid))
 		local = NULL; /* local_sha1 == null_sha1 indicates unborn ref */
-	else if (!(local = lookup_commit_reference(local_oid.hash)))
+	else if (!(local = lookup_commit_reference(&local_oid)))
 		die("Could not parse local commit %s (%s)",
 		    oid_to_hex(&local_oid), o->local_ref);
 	trace_printf("\tlocal commit: %.7s\n", oid_to_hex(&local_oid));
@@ -572,7 +572,7 @@ int notes_merge(struct notes_merge_options *o,
 			die("Failed to resolve remote notes ref '%s'",
 			    o->remote_ref);
 		}
-	} else if (!(remote = lookup_commit_reference(remote_oid.hash))) {
+	} else if (!(remote = lookup_commit_reference(&remote_oid))) {
 		die("Could not parse remote commit %s (%s)",
 		    oid_to_hex(&remote_oid), o->remote_ref);
 	}