Merge branch 'rs/ref-transaction-0'

Early part of the "ref transaction" topic.

* rs/ref-transaction-0:
  refs.c: change ref_transaction_update() to do error checking and return status
  refs.c: remove the onerr argument to ref_transaction_commit
  update-ref: use err argument to get error from ref_transaction_commit
  refs.c: make update_ref_write update a strbuf on failure
  refs.c: make ref_update_reject_duplicates take a strbuf argument for errors
  refs.c: log_ref_write should try to return meaningful errno
  refs.c: make resolve_ref_unsafe set errno to something meaningful on error
  refs.c: commit_packed_refs to return a meaningful errno on failure
  refs.c: make remove_empty_directories always set errno to something sane
  refs.c: verify_lock should set errno to something meaningful
  refs.c: make sure log_ref_setup returns a meaningful errno
  refs.c: add an err argument to repack_without_refs
  lockfile.c: make lock_file return a meaningful errno on failurei
  lockfile.c: add a new public function unable_to_lock_message
  refs.c: add a strbuf argument to ref_transaction_commit for error logging
  refs.c: allow passing NULL to ref_transaction_free
  refs.c: constify the sha arguments for ref_transaction_create|delete|update
  refs.c: ref_transaction_commit should not free the transaction
  refs.c: remove ref_transaction_rollback

refs.c

@@ -1533,6 +1533,7 @@ static const char *handle_missing_loose_ref(const char *refname,
 	}
 }
 
+/* This function needs to return a meaningful errno on failure */
 const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int reading, int *flag)
 {
 	int depth = MAXDEPTH;
@@ -1543,8 +1544,10 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 	if (flag)
 		*flag = 0;
 
-	if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL))
+	if (check_refname_format(refname, REFNAME_ALLOW_ONELEVEL)) {
+		errno = EINVAL;
 		return NULL;
+	}
 
 	for (;;) {
 		char path[PATH_MAX];
@@ -1552,8 +1555,10 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 		char *buf;
 		int fd;
 
-		if (--depth < 0)
+		if (--depth < 0) {
+			errno = ELOOP;
 			return NULL;
+		}
 
 		git_snpath(path, sizeof(path), "%s", refname);
 
@@ -1615,9 +1620,13 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 				return NULL;
 		}
 		len = read_in_full(fd, buffer, sizeof(buffer)-1);
-		close(fd);
-		if (len < 0)
+		if (len < 0) {
+			int save_errno = errno;
+			close(fd);
+			errno = save_errno;
 			return NULL;
+		}
+		close(fd);
 		while (len && isspace(buffer[len-1]))
 			len--;
 		buffer[len] = '\0';
@@ -1634,6 +1643,7 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 			    (buffer[40] != '\0' && !isspace(buffer[40]))) {
 				if (flag)
 					*flag |= REF_ISBROKEN;
+				errno = EINVAL;
 				return NULL;
 			}
 			return refname;
@@ -1646,6 +1656,7 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 		if (check_refname_format(buf, REFNAME_ALLOW_ONELEVEL)) {
 			if (flag)
 				*flag |= REF_ISBROKEN;
+			errno = EINVAL;
 			return NULL;
 		}
 		refname = strcpy(refname_buffer, buf);
@@ -2131,18 +2142,22 @@ int refname_match(const char *abbrev_name, const char *full_name)
 	return 0;
 }
 
+/* This function should make sure errno is meaningful on error */
 static struct ref_lock *verify_lock(struct ref_lock *lock,
 	const unsigned char *old_sha1, int mustexist)
 {
 	if (read_ref_full(lock->ref_name, lock->old_sha1, mustexist, NULL)) {
+		int save_errno = errno;
 		error("Can't verify ref %s", lock->ref_name);
 		unlock_ref(lock);
+		errno = save_errno;
 		return NULL;
 	}
 	if (hashcmp(lock->old_sha1, old_sha1)) {
 		error("Ref %s is at %s but expected %s", lock->ref_name,
 			sha1_to_hex(lock->old_sha1), sha1_to_hex(old_sha1));
 		unlock_ref(lock);
+		errno = EBUSY;
 		return NULL;
 	}
 	return lock;
@@ -2155,14 +2170,16 @@ static int remove_empty_directories(const char *file)
 	 * only empty directories), remove them.
 	 */
 	struct strbuf path;
-	int result;
+	int result, save_errno;
 
 	strbuf_init(&path, 20);
 	strbuf_addstr(&path, file);
 
 	result = remove_dir_recursively(&path, REMOVE_DIR_EMPTY_ONLY);
+	save_errno = errno;
 
 	strbuf_release(&path);
+	errno = save_errno;
 
 	return result;
 }
@@ -2251,6 +2268,7 @@ int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
 	return logs_found;
 }
 
+/* This function should make sure errno is meaningful on error */
 static struct ref_lock *lock_ref_sha1_basic(const char *refname,
 					    const unsigned char *old_sha1,
 					    int flags, int *type_p)
@@ -2411,6 +2429,7 @@ static int write_packed_entry_fn(struct ref_entry *entry, void *cb_data)
 	return 0;
 }
 
+/* This should return a meaningful errno on failure */
 int lock_packed_refs(int flags)
 {
 	struct packed_ref_cache *packed_ref_cache;
@@ -2430,11 +2449,16 @@ int lock_packed_refs(int flags)
 	return 0;
 }
 
+/*
+ * Commit the packed refs changes.
+ * On error we must make sure that errno contains a meaningful value.
+ */
 int commit_packed_refs(void)
 {
 	struct packed_ref_cache *packed_ref_cache =
 		get_packed_ref_cache(&ref_cache);
 	int error = 0;
+	int save_errno = 0;
 
 	if (!packed_ref_cache->lock)
 		die("internal error: packed-refs not locked");
@@ -2444,10 +2468,13 @@ int commit_packed_refs(void)
 	do_for_each_entry_in_dir(get_packed_ref_dir(packed_ref_cache),
 				 0, write_packed_entry_fn,
 				 &packed_ref_cache->lock->fd);
-	if (commit_lock_file(packed_ref_cache->lock))
+	if (commit_lock_file(packed_ref_cache->lock)) {
+		save_errno = errno;
 		error = -1;
+	}
 	packed_ref_cache->lock = NULL;
 	release_packed_ref_cache(packed_ref_cache);
+	errno = save_errno;
 	return error;
 }
 
@@ -2654,12 +2681,12 @@ static int curate_packed_ref_fn(struct ref_entry *entry, void *cb_data)
 	return 0;
 }
 
-int repack_without_refs(const char **refnames, int n)
+int repack_without_refs(const char **refnames, int n, struct strbuf *err)
 {
 	struct ref_dir *packed;
 	struct string_list refs_to_delete = STRING_LIST_INIT_DUP;
 	struct string_list_item *ref_to_delete;
-	int i, removed = 0;
+	int i, ret, removed = 0;
 
 	/* Look for a packed ref */
 	for (i = 0; i < n; i++)
@@ -2671,6 +2698,11 @@ int repack_without_refs(const char **refnames, int n)
 		return 0; /* no refname exists in packed refs */
 
 	if (lock_packed_refs(0)) {
+		if (err) {
+			unable_to_lock_message(git_path("packed-refs"), errno,
+					       err);
+			return -1;
+		}
 		unable_to_lock_error(git_path("packed-refs"), errno);
 		return error("cannot delete '%s' from packed refs", refnames[i]);
 	}
@@ -2697,12 +2729,16 @@ int repack_without_refs(const char **refnames, int n)
 	}
 
 	/* Write what remains */
-	return commit_packed_refs();
+	ret = commit_packed_refs();
+	if (ret && err)
+		strbuf_addf(err, "unable to overwrite old ref-pack file: %s",
+			    strerror(errno));
+	return ret;
 }
 
 static int repack_without_ref(const char *refname)
 {
-	return repack_without_refs(&refname, 1);
+	return repack_without_refs(&refname, 1, NULL);
 }
 
 static int delete_ref_loose(struct ref_lock *lock, int flag)
@@ -2940,6 +2976,7 @@ static int copy_msg(char *buf, const char *msg)
 	return cp - buf;
 }
 
+/* This function must set a meaningful errno on failure */
 int log_ref_setup(const char *refname, char *logfile, int bufsize)
 {
 	int logfd, oflags = O_APPEND | O_WRONLY;
@@ -2950,9 +2987,12 @@ int log_ref_setup(const char *refname, char *logfile, int bufsize)
 	     starts_with(refname, "refs/remotes/") ||
 	     starts_with(refname, "refs/notes/") ||
 	     !strcmp(refname, "HEAD"))) {
-		if (safe_create_leading_directories(logfile) < 0)
-			return error("unable to create directory for %s",
-				     logfile);
+		if (safe_create_leading_directories(logfile) < 0) {
+			int save_errno = errno;
+			error("unable to create directory for %s", logfile);
+			errno = save_errno;
+			return -1;
+		}
 		oflags |= O_CREAT;
 	}
 
@@ -2963,15 +3003,22 @@ int log_ref_setup(const char *refname, char *logfile, int bufsize)
 
 		if ((oflags & O_CREAT) && errno == EISDIR) {
 			if (remove_empty_directories(logfile)) {
-				return error("There are still logs under '%s'",
-					     logfile);
+				int save_errno = errno;
+				error("There are still logs under '%s'",
+				      logfile);
+				errno = save_errno;
+				return -1;
 			}
 			logfd = open(logfile, oflags, 0666);
 		}
 
-		if (logfd < 0)
-			return error("Unable to append to %s: %s",
-				     logfile, strerror(errno));
+		if (logfd < 0) {
+			int save_errno = errno;
+			error("Unable to append to %s: %s", logfile,
+			      strerror(errno));
+			errno = save_errno;
+			return -1;
+		}
 	}
 
 	adjust_shared_perm(logfile);
@@ -3011,8 +3058,19 @@ static int log_ref_write(const char *refname, const unsigned char *old_sha1,
 		len += copy_msg(logrec + len - 1, msg) - 1;
 	written = len <= maxlen ? write_in_full(logfd, logrec, len) : -1;
 	free(logrec);
-	if (close(logfd) != 0 || written != len)
-		return error("Unable to append to %s", log_file);
+	if (written != len) {
+		int save_errno = errno;
+		close(logfd);
+		error("Unable to append to %s", log_file);
+		errno = save_errno;
+		return -1;
+	}
+	if (close(logfd)) {
+		int save_errno = errno;
+		error("Unable to append to %s", log_file);
+		errno = save_errno;
+		return -1;
+	}
 	return 0;
 }
 
@@ -3021,14 +3079,17 @@ static int is_branch(const char *refname)
 	return !strcmp(refname, "HEAD") || starts_with(refname, "refs/heads/");
 }
 
+/* This function must return a meaningful errno */
 int write_ref_sha1(struct ref_lock *lock,
 	const unsigned char *sha1, const char *logmsg)
 {
 	static char term = '\n';
 	struct object *o;
 
-	if (!lock)
+	if (!lock) {
+		errno = EINVAL;
 		return -1;
+	}
 	if (!lock->force_write && !hashcmp(lock->old_sha1, sha1)) {
 		unlock_ref(lock);
 		return 0;
@@ -3038,19 +3099,23 @@ int write_ref_sha1(struct ref_lock *lock,
 		error("Trying to write ref %s with nonexistent object %s",
 			lock->ref_name, sha1_to_hex(sha1));
 		unlock_ref(lock);
+		errno = EINVAL;
 		return -1;
 	}
 	if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) {
 		error("Trying to write non-commit object %s to branch %s",
 			sha1_to_hex(sha1), lock->ref_name);
 		unlock_ref(lock);
+		errno = EINVAL;
 		return -1;
 	}
 	if (write_in_full(lock->lock_fd, sha1_to_hex(sha1), 40) != 40 ||
-	    write_in_full(lock->lock_fd, &term, 1) != 1
-		|| close_ref(lock) < 0) {
+	    write_in_full(lock->lock_fd, &term, 1) != 1 ||
+	    close_ref(lock) < 0) {
+		int save_errno = errno;
 		error("Couldn't write %s", lock->lk->filename);
 		unlock_ref(lock);
+		errno = save_errno;
 		return -1;
 	}
 	clear_loose_ref_cache(&ref_cache);
@@ -3487,10 +3552,13 @@ static struct ref_lock *update_ref_lock(const char *refname,
 
 static int update_ref_write(const char *action, const char *refname,
 			    const unsigned char *sha1, struct ref_lock *lock,
-			    enum action_on_err onerr)
+			    struct strbuf *err, enum action_on_err onerr)
 {
 	if (write_ref_sha1(lock, sha1, action) < 0) {
 		const char *str = "Cannot update the ref '%s'.";
+		if (err)
+			strbuf_addf(err, str, refname);
+
 		switch (onerr) {
 		case UPDATE_REFS_MSG_ON_ERR: error(str, refname); break;
 		case UPDATE_REFS_DIE_ON_ERR: die(str, refname); break;
@@ -3533,10 +3601,13 @@ struct ref_transaction *ref_transaction_begin(void)
 	return xcalloc(1, sizeof(struct ref_transaction));
 }
 
-static void ref_transaction_free(struct ref_transaction *transaction)
+void ref_transaction_free(struct ref_transaction *transaction)
 {
 	int i;
 
+	if (!transaction)
+		return;
+
 	for (i = 0; i < transaction->nr; i++)
 		free(transaction->updates[i]);
 
@@ -3544,11 +3615,6 @@ static void ref_transaction_free(struct ref_transaction *transaction)
 	free(transaction);
 }
 
-void ref_transaction_rollback(struct ref_transaction *transaction)
-{
-	ref_transaction_free(transaction);
-}
-
 static struct ref_update *add_update(struct ref_transaction *transaction,
 				     const char *refname)
 {
@@ -3561,23 +3627,30 @@ static struct ref_update *add_update(struct ref_transaction *transaction,
 	return update;
 }
 
-void ref_transaction_update(struct ref_transaction *transaction,
-			    const char *refname,
-			    unsigned char *new_sha1, unsigned char *old_sha1,
-			    int flags, int have_old)
+int ref_transaction_update(struct ref_transaction *transaction,
+			   const char *refname,
+			   const unsigned char *new_sha1,
+			   const unsigned char *old_sha1,
+			   int flags, int have_old,
+			   struct strbuf *err)
 {
-	struct ref_update *update = add_update(transaction, refname);
+	struct ref_update *update;
 
+	if (have_old && !old_sha1)
+		die("BUG: have_old is true but old_sha1 is NULL");
+
+	update = add_update(transaction, refname);
 	hashcpy(update->new_sha1, new_sha1);
 	update->flags = flags;
 	update->have_old = have_old;
 	if (have_old)
 		hashcpy(update->old_sha1, old_sha1);
+	return 0;
 }
 
 void ref_transaction_create(struct ref_transaction *transaction,
 			    const char *refname,
-			    unsigned char *new_sha1,
+			    const unsigned char *new_sha1,
 			    int flags)
 {
 	struct ref_update *update = add_update(transaction, refname);
@@ -3591,7 +3664,7 @@ void ref_transaction_create(struct ref_transaction *transaction,
 
 void ref_transaction_delete(struct ref_transaction *transaction,
 			    const char *refname,
-			    unsigned char *old_sha1,
+			    const unsigned char *old_sha1,
 			    int flags, int have_old)
 {
 	struct ref_update *update = add_update(transaction, refname);
@@ -3612,7 +3685,7 @@ int update_ref(const char *action, const char *refname,
 	lock = update_ref_lock(refname, oldval, flags, NULL, onerr);
 	if (!lock)
 		return 1;
-	return update_ref_write(action, refname, sha1, lock, onerr);
+	return update_ref_write(action, refname, sha1, lock, NULL, onerr);
 }
 
 static int ref_update_compare(const void *r1, const void *r2)
@@ -3623,28 +3696,23 @@ static int ref_update_compare(const void *r1, const void *r2)
 }
 
 static int ref_update_reject_duplicates(struct ref_update **updates, int n,
-					enum action_on_err onerr)
+					struct strbuf *err)
 {
 	int i;
 	for (i = 1; i < n; i++)
 		if (!strcmp(updates[i - 1]->refname, updates[i]->refname)) {
 			const char *str =
 				"Multiple updates for ref '%s' not allowed.";
-			switch (onerr) {
-			case UPDATE_REFS_MSG_ON_ERR:
-				error(str, updates[i]->refname); break;
-			case UPDATE_REFS_DIE_ON_ERR:
-				die(str, updates[i]->refname); break;
-			case UPDATE_REFS_QUIET_ON_ERR:
-				break;
-			}
+			if (err)
+				strbuf_addf(err, str, updates[i]->refname);
+
 			return 1;
 		}
 	return 0;
 }
 
 int ref_transaction_commit(struct ref_transaction *transaction,
-			   const char *msg, enum action_on_err onerr)
+			   const char *msg, struct strbuf *err)
 {
 	int ret = 0, delnum = 0, i;
 	const char **delnames;
@@ -3659,7 +3727,7 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 
 	/* Copy, sort, and reject duplicate refs */
 	qsort(updates, n, sizeof(*updates), ref_update_compare);
-	ret = ref_update_reject_duplicates(updates, n, onerr);
+	ret = ref_update_reject_duplicates(updates, n, err);
 	if (ret)
 		goto cleanup;
 
@@ -3671,8 +3739,12 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 					       (update->have_old ?
 						update->old_sha1 : NULL),
 					       update->flags,
-					       &update->type, onerr);
+					       &update->type,
+					       UPDATE_REFS_QUIET_ON_ERR);
 		if (!update->lock) {
+			if (err)
+				strbuf_addf(err, "Cannot lock the ref '%s'.",
+					    update->refname);
 			ret = 1;
 			goto cleanup;
 		}
@@ -3686,7 +3758,8 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 			ret = update_ref_write(msg,
 					       update->refname,
 					       update->new_sha1,
-					       update->lock, onerr);
+					       update->lock, err,
+					       UPDATE_REFS_QUIET_ON_ERR);
 			update->lock = NULL; /* freed by update_ref_write */
 			if (ret)
 				goto cleanup;
@@ -3703,7 +3776,7 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 		}
 	}
 
-	ret |= repack_without_refs(delnames, delnum);
+	ret |= repack_without_refs(delnames, delnum, err);
 	for (i = 0; i < delnum; i++)
 		unlink_or_warn(git_path("logs/%s", delnames[i]));
 	clear_loose_ref_cache(&ref_cache);
@@ -3713,7 +3786,6 @@ cleanup:
 		if (updates[i]->lock)
 			unlock_ref(updates[i]->lock);
 	free(delnames);
-	ref_transaction_free(transaction);
 	return ret;
 }