1 files changed, 150 insertions, 45 deletions

diff --git a/refs.c b/refs.c
index 2c6509d..6898263 100644
--- a/refs.c
+++ b/refs.c
@@ -3252,9 +3252,9 @@ static struct ref_lock *update_ref_lock(const char *refname,
 	if (!lock) {
 		const char *str = "Cannot lock the ref '%s'.";
 		switch (onerr) {
-		case MSG_ON_ERR: error(str, refname); break;
-		case DIE_ON_ERR: die(str, refname); break;
-		case QUIET_ON_ERR: break;
+		case UPDATE_REFS_MSG_ON_ERR: error(str, refname); break;
+		case UPDATE_REFS_DIE_ON_ERR: die(str, refname); break;
+		case UPDATE_REFS_QUIET_ON_ERR: break;
 		}
 	}
 	return lock;
@@ -3267,15 +3267,118 @@ static int update_ref_write(const char *action, const char *refname,
 	if (write_ref_sha1(lock, sha1, action) < 0) {
 		const char *str = "Cannot update the ref '%s'.";
 		switch (onerr) {
-		case MSG_ON_ERR: error(str, refname); break;
-		case DIE_ON_ERR: die(str, refname); break;
-		case QUIET_ON_ERR: break;
+		case UPDATE_REFS_MSG_ON_ERR: error(str, refname); break;
+		case UPDATE_REFS_DIE_ON_ERR: die(str, refname); break;
+		case UPDATE_REFS_QUIET_ON_ERR: break;
 		}
 		return 1;
 	}
 	return 0;
 }
 
+/**
+ * Information needed for a single ref update.  Set new_sha1 to the
+ * new value or to zero to delete the ref.  To check the old value
+ * while locking the ref, set have_old to 1 and set old_sha1 to the
+ * value or to zero to ensure the ref does not exist before update.
+ */
+struct ref_update {
+	unsigned char new_sha1[20];
+	unsigned char old_sha1[20];
+	int flags; /* REF_NODEREF? */
+	int have_old; /* 1 if old_sha1 is valid, 0 otherwise */
+	struct ref_lock *lock;
+	int type;
+	const char refname[FLEX_ARRAY];
+};
+
+/*
+ * Data structure for holding a reference transaction, which can
+ * consist of checks and updates to multiple references, carried out
+ * as atomically as possible.  This structure is opaque to callers.
+ */
+struct ref_transaction {
+	struct ref_update **updates;
+	size_t alloc;
+	size_t nr;
+};
+
+struct ref_transaction *ref_transaction_begin(void)
+{
+	return xcalloc(1, sizeof(struct ref_transaction));
+}
+
+static void ref_transaction_free(struct ref_transaction *transaction)
+{
+	int i;
+
+	for (i = 0; i < transaction->nr; i++)
+		free(transaction->updates[i]);
+
+	free(transaction->updates);
+	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)
+{
+	size_t len = strlen(refname);
+	struct ref_update *update = xcalloc(1, sizeof(*update) + len + 1);
+
+	strcpy((char *)update->refname, refname);
+	ALLOC_GROW(transaction->updates, transaction->nr + 1, transaction->alloc);
+	transaction->updates[transaction->nr++] = update;
+	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)
+{
+	struct ref_update *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);
+}
+
+void ref_transaction_create(struct ref_transaction *transaction,
+			    const char *refname,
+			    unsigned char *new_sha1,
+			    int flags)
+{
+	struct ref_update *update = add_update(transaction, refname);
+
+	assert(!is_null_sha1(new_sha1));
+	hashcpy(update->new_sha1, new_sha1);
+	hashclr(update->old_sha1);
+	update->flags = flags;
+	update->have_old = 1;
+}
+
+void ref_transaction_delete(struct ref_transaction *transaction,
+			    const char *refname,
+			    unsigned char *old_sha1,
+			    int flags, int have_old)
+{
+	struct ref_update *update = add_update(transaction, refname);
+
+	update->flags = flags;
+	update->have_old = have_old;
+	if (have_old) {
+		assert(!is_null_sha1(old_sha1));
+		hashcpy(update->old_sha1, old_sha1);
+	}
+}
+
 int update_ref(const char *action, const char *refname,
 	       const unsigned char *sha1, const unsigned char *oldval,
 	       int flags, enum action_on_err onerr)
@@ -3291,7 +3394,7 @@ static int ref_update_compare(const void *r1, const void *r2)
 {
 	const struct ref_update * const *u1 = r1;
 	const struct ref_update * const *u2 = r2;
-	return strcmp((*u1)->ref_name, (*u2)->ref_name);
+	return strcmp((*u1)->refname, (*u2)->refname);
 }
 
 static int ref_update_reject_duplicates(struct ref_update **updates, int n,
@@ -3299,15 +3402,15 @@ static int ref_update_reject_duplicates(struct ref_update **updates, int n,
 {
 	int i;
 	for (i = 1; i < n; i++)
-		if (!strcmp(updates[i - 1]->ref_name, updates[i]->ref_name)) {
+		if (!strcmp(updates[i - 1]->refname, updates[i]->refname)) {
 			const char *str =
 				"Multiple updates for ref '%s' not allowed.";
 			switch (onerr) {
-			case MSG_ON_ERR:
-				error(str, updates[i]->ref_name); break;
-			case DIE_ON_ERR:
-				die(str, updates[i]->ref_name); break;
-			case QUIET_ON_ERR:
+			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;
 			}
 			return 1;
@@ -3315,26 +3418,21 @@ static int ref_update_reject_duplicates(struct ref_update **updates, int n,
 	return 0;
 }
 
-int update_refs(const char *action, const struct ref_update **updates_orig,
-		int n, enum action_on_err onerr)
+int ref_transaction_commit(struct ref_transaction *transaction,
+			   const char *msg, enum action_on_err onerr)
 {
 	int ret = 0, delnum = 0, i;
-	struct ref_update **updates;
-	int *types;
-	struct ref_lock **locks;
 	const char **delnames;
+	int n = transaction->nr;
+	struct ref_update **updates = transaction->updates;
 
-	if (!updates_orig || !n)
+	if (!n)
 		return 0;
 
 	/* Allocate work space */
-	updates = xmalloc(sizeof(*updates) * n);
-	types = xmalloc(sizeof(*types) * n);
-	locks = xcalloc(n, sizeof(*locks));
 	delnames = xmalloc(sizeof(*delnames) * n);
 
 	/* Copy, sort, and reject duplicate refs */
-	memcpy(updates, updates_orig, sizeof(*updates) * n);
 	qsort(updates, n, sizeof(*updates), ref_update_compare);
 	ret = ref_update_reject_duplicates(updates, n, onerr);
 	if (ret)
@@ -3342,35 +3440,44 @@ int update_refs(const char *action, const struct ref_update **updates_orig,
 
 	/* Acquire all locks while verifying old values */
 	for (i = 0; i < n; i++) {
-		locks[i] = update_ref_lock(updates[i]->ref_name,
-					   (updates[i]->have_old ?
-					    updates[i]->old_sha1 : NULL),
-					   updates[i]->flags,
-					   &types[i], onerr);
-		if (!locks[i]) {
+		struct ref_update *update = updates[i];
+
+		update->lock = update_ref_lock(update->refname,
+					       (update->have_old ?
+						update->old_sha1 : NULL),
+					       update->flags,
+					       &update->type, onerr);
+		if (!update->lock) {
 			ret = 1;
 			goto cleanup;
 		}
 	}
 
 	/* Perform updates first so live commits remain referenced */
-	for (i = 0; i < n; i++)
-		if (!is_null_sha1(updates[i]->new_sha1)) {
-			ret = update_ref_write(action,
-					       updates[i]->ref_name,
-					       updates[i]->new_sha1,
-					       locks[i], onerr);
-			locks[i] = NULL; /* freed by update_ref_write */
+	for (i = 0; i < n; i++) {
+		struct ref_update *update = updates[i];
+
+		if (!is_null_sha1(update->new_sha1)) {
+			ret = update_ref_write(msg,
+					       update->refname,
+					       update->new_sha1,
+					       update->lock, onerr);
+			update->lock = NULL; /* freed by update_ref_write */
 			if (ret)
 				goto cleanup;
 		}
+	}
 
 	/* Perform deletes now that updates are safely completed */
-	for (i = 0; i < n; i++)
-		if (locks[i]) {
-			delnames[delnum++] = locks[i]->ref_name;
-			ret |= delete_ref_loose(locks[i], types[i]);
+	for (i = 0; i < n; i++) {
+		struct ref_update *update = updates[i];
+
+		if (update->lock) {
+			delnames[delnum++] = update->lock->ref_name;
+			ret |= delete_ref_loose(update->lock, update->type);
 		}
+	}
+
 	ret |= repack_without_refs(delnames, delnum);
 	for (i = 0; i < delnum; i++)
 		unlink_or_warn(git_path("logs/%s", delnames[i]));
@@ -3378,12 +3485,10 @@ int update_refs(const char *action, const struct ref_update **updates_orig,
 
 cleanup:
 	for (i = 0; i < n; i++)
-		if (locks[i])
-			unlock_ref(locks[i]);
-	free(updates);
-	free(types);
-	free(locks);
+		if (updates[i]->lock)
+			unlock_ref(updates[i]->lock);
 	free(delnames);
+	ref_transaction_free(transaction);
 	return ret;
 }