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/builtin/branch.c b/builtin/branch.c
index 48a513a..83fcda4 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -124,7 +124,7 @@ static int branch_merged(int kind, const char *name,
 		    (reference_name = reference_name_to_free =
 		     resolve_refdup(upstream, RESOLVE_REF_READING,
 				    oid.hash, NULL)) != NULL)
-			reference_rev = lookup_commit_reference(oid.hash);
+			reference_rev = lookup_commit_reference(&oid);
 	}
 	if (!reference_rev)
 		reference_rev = head_rev;
@@ -157,7 +157,7 @@ static int check_branch_commit(const char *branchname, const char *refname,
 			       const struct object_id *oid, struct commit *head_rev,
 			       int kinds, int force)
 {
-	struct commit *rev = lookup_commit_reference(oid->hash);
+	struct commit *rev = lookup_commit_reference(oid);
 	if (!rev) {
 		error(_("Couldn't look up commit object for '%s'"), refname);
 		return -1;
@@ -211,7 +211,7 @@ static int delete_branches(int argc, const char **argv, int force, int kinds,
 	}
 
 	if (!force) {
-		head_rev = lookup_commit_reference(head_oid.hash);
+		head_rev = lookup_commit_reference(&head_oid);
 		if (!head_rev)
 			die(_("Couldn't look up commit object for HEAD"));
 	}