Merge branch 'mh/refs-have-new'

Simplify the ref transaction API around how "the ref should be
pointing at this object" is specified.

* mh/refs-have-new:
  refs.h: remove duplication in function docstrings
  update_ref(): improve documentation
  ref_transaction_verify(): new function to check a reference's value
  ref_transaction_delete(): check that old_sha1 is not null_sha1
  ref_transaction_create(): check that new_sha1 is valid
  commit: avoid race when creating orphan commits
  commit: add tests of commit races
  ref_transaction_delete(): remove "have_old" parameter
  ref_transaction_update(): remove "have_old" parameter
  struct ref_update: move "have_old" into "flags"
  refs.c: change some "flags" to "unsigned int"
  refs: remove the gap in the REF_* constant values
  refs: move REF_DELETING to refs.c

branch.c

@@ -284,8 +284,9 @@ void create_branch(const char *head,
 
 		transaction = ref_transaction_begin(&err);
 		if (!transaction ||
-		    ref_transaction_update(transaction, ref.buf, sha1,
-					   null_sha1, 0, !forcing, msg, &err) ||
+		    ref_transaction_update(transaction, ref.buf,
+					   sha1, forcing ? NULL : null_sha1,
+					   0, msg, &err) ||
 		    ref_transaction_commit(transaction, &err))
 			die("%s", err.buf);
 		ref_transaction_free(transaction);

builtin/commit.c

@@ -1766,8 +1766,8 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 	if (!transaction ||
 	    ref_transaction_update(transaction, "HEAD", sha1,
 				   current_head
-				   ? current_head->object.sha1 : NULL,
-				   0, !!current_head, sb.buf, &err) ||
+				   ? current_head->object.sha1 : null_sha1,
+				   0, sb.buf, &err) ||
 	    ref_transaction_commit(transaction, &err)) {
 		rollback_index_files();
 		die("%s", err.buf);

builtin/fetch.c

@@ -415,8 +415,10 @@ static int s_update_ref(const char *action,
 
 	transaction = ref_transaction_begin(&err);
 	if (!transaction ||
-	    ref_transaction_update(transaction, ref->name, ref->new_sha1,
-				   ref->old_sha1, 0, check_old, msg, &err))
+	    ref_transaction_update(transaction, ref->name,
+				   ref->new_sha1,
+				   check_old ? ref->old_sha1 : NULL,
+				   0, msg, &err))
 		goto fail;
 
 	ret = ref_transaction_commit(transaction, &err);

builtin/receive-pack.c

@@ -953,8 +953,7 @@ static const char *update(struct command *cmd, struct shallow_info *si)
 		if (ref_transaction_delete(transaction,
 					   namespaced_name,
 					   old_sha1,
-					   0, old_sha1 != NULL,
-					   "push", &err)) {
+					   0, "push", &err)) {
 			rp_error("%s", err.buf);
 			strbuf_release(&err);
 			return "failed to delete";
@@ -971,7 +970,7 @@ static const char *update(struct command *cmd, struct shallow_info *si)
 		if (ref_transaction_update(transaction,
 					   namespaced_name,
 					   new_sha1, old_sha1,
-					   0, 1, "push",
+					   0, "push",
 					   &err)) {
 			rp_error("%s", err.buf);
 			strbuf_release(&err);

builtin/replace.c

@@ -172,7 +172,7 @@ static int replace_object_sha1(const char *object_ref,
 	transaction = ref_transaction_begin(&err);
 	if (!transaction ||
 	    ref_transaction_update(transaction, ref, repl, prev,
-				   0, 1, NULL, &err) ||
+				   0, NULL, &err) ||
 	    ref_transaction_commit(transaction, &err))
 		die("%s", err.buf);
 

builtin/tag.c

@@ -733,7 +733,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 	transaction = ref_transaction_begin(&err);
 	if (!transaction ||
 	    ref_transaction_update(transaction, ref.buf, object, prev,
-				   0, 1, NULL, &err) ||
+				   0, NULL, &err) ||
 	    ref_transaction_commit(transaction, &err))
 		die("%s", err.buf);
 	ref_transaction_free(transaction);

builtin/update-ref.c

@@ -198,8 +198,9 @@ static const char *parse_cmd_update(struct ref_transaction *transaction,
 	if (*next != line_termination)
 		die("update %s: extra input: %s", refname, next);
 
-	if (ref_transaction_update(transaction, refname, new_sha1, old_sha1,
-				   update_flags, have_old, msg, &err))
+	if (ref_transaction_update(transaction, refname,
+				   new_sha1, have_old ? old_sha1 : NULL,
+				   update_flags, msg, &err))
 		die("%s", err.buf);
 
 	update_flags = 0;
@@ -264,8 +265,9 @@ static const char *parse_cmd_delete(struct ref_transaction *transaction,
 	if (*next != line_termination)
 		die("delete %s: extra input: %s", refname, next);
 
-	if (ref_transaction_delete(transaction, refname, old_sha1,
-				   update_flags, have_old, msg, &err))
+	if (ref_transaction_delete(transaction, refname,
+				   have_old ? old_sha1 : NULL,
+				   update_flags, msg, &err))
 		die("%s", err.buf);
 
 	update_flags = 0;
@@ -280,7 +282,6 @@ static const char *parse_cmd_verify(struct ref_transaction *transaction,
 {
 	struct strbuf err = STRBUF_INIT;
 	char *refname;
-	unsigned char new_sha1[20];
 	unsigned char old_sha1[20];
 
 	refname = parse_refname(input, &next);
@@ -291,13 +292,11 @@ static const char *parse_cmd_verify(struct ref_transaction *transaction,
 			    PARSE_SHA1_OLD))
 		hashclr(old_sha1);
 
-	hashcpy(new_sha1, old_sha1);
-
 	if (*next != line_termination)
 		die("verify %s: extra input: %s", refname, next);
 
-	if (ref_transaction_update(transaction, refname, new_sha1, old_sha1,
-				   update_flags, 1, msg, &err))
+	if (ref_transaction_verify(transaction, refname, old_sha1,
+				   update_flags, &err))
 		die("%s", err.buf);
 
 	update_flags = 0;
@@ -353,7 +352,8 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 {
 	const char *refname, *oldval;
 	unsigned char sha1[20], oldsha1[20];
-	int delete = 0, no_deref = 0, read_stdin = 0, end_null = 0, flags = 0;
+	int delete = 0, no_deref = 0, read_stdin = 0, end_null = 0;
+	unsigned int flags = 0;
 	struct option options[] = {
 		OPT_STRING( 'm', NULL, &msg, N_("reason"), N_("reason of the update")),
 		OPT_BOOL('d', NULL, &delete, N_("delete the reference")),

cache.h

@@ -568,7 +568,7 @@ extern void update_index_if_able(struct index_state *, struct lock_file *);
 extern int hold_locked_index(struct lock_file *, int);
 extern void set_alternate_index_output(const char *);
 
-extern int delete_ref(const char *, const unsigned char *sha1, int delopt);
+extern int delete_ref(const char *, const unsigned char *sha1, unsigned int flags);
 
 /* Environment bits from configuration mechanism */
 extern int trust_executable_bit;

fast-import.c

@@ -1720,7 +1720,7 @@ static int update_branch(struct branch *b)
 	transaction = ref_transaction_begin(&err);
 	if (!transaction ||
 	    ref_transaction_update(transaction, b->name, b->sha1, old_sha1,
-				   0, 1, msg, &err) ||
+				   0, msg, &err) ||
 	    ref_transaction_commit(transaction, &err)) {
 		ref_transaction_free(transaction);
 		error("%s", err.buf);
@@ -1760,8 +1760,8 @@ static void dump_tags(void)
 		strbuf_reset(&ref_name);
 		strbuf_addf(&ref_name, "refs/tags/%s", t->name);
 
-		if (ref_transaction_update(transaction, ref_name.buf, t->sha1,
-					   NULL, 0, 0, msg, &err)) {
+		if (ref_transaction_update(transaction, ref_name.buf,
+					   t->sha1, NULL, 0, msg, &err)) {
 			failure |= error("%s", err.buf);
 			goto cleanup;
 		}