[PATCH v6 40/42] refs.c: pass a skip list to name_conflict_fn

[Ronnie Sahlberg <sahlberg@google.com>]

Allow passing a list of refs to ckip checking to name_conflict_fn.
There are some conditions where we want to allow a temporary conflict and skip
checking those refs. For example if we have a transaction that
1, guarantees that m is a packed refs and there is no loose ref for m
2, the transaction will delete m from the packed ref
3, the transaction will create conflicting m/m

For this case we want to be able to lock anc create m/m since we know that the
conflict is only transient. I.e. the conflict will be automatically resolved
by the transaction when it deletes m.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 refs.c | 43 +++++++++++++++++++++++++++++++++----------
 1 file changed, 33 insertions(+), 10 deletions(-)

diff --git a/refs.c b/refs.c
index b525076..eb75927 100644
--- a/refs.c
+++ b/refs.c
@@ -789,11 +789,19 @@ struct name_conflict_cb {
 	const char *refname;
 	const char *oldrefname;
 	const char *conflicting_refname;
+	const char **skip;
+	int skipnum;
 };
 
 static int name_conflict_fn(struct ref_entry *entry, void *cb_data)
 {
 	struct name_conflict_cb *data = (struct name_conflict_cb *)cb_data;
+	int i;
+	for(i = 0; i < data->skipnum; i++) {
+		if (!strcmp(entry->name, data->skip[i])) {
+			return 0;
+		}
+	}
 	if (data->oldrefname && !strcmp(data->oldrefname, entry->name))
 		return 0;
 	if (names_conflict(data->refname, entry->name)) {
@@ -808,15 +816,21 @@ static int name_conflict_fn(struct ref_entry *entry, void *cb_data)
  * conflicting with the name of an existing reference in dir.  If
  * oldrefname is non-NULL, ignore potential conflicts with oldrefname
  * (e.g., because oldrefname is scheduled for deletion in the same
- * operation).
+ * operation). skip contains a list of refs we want to skip checking for
+ * conflicts with. Refs may be skipped due to us knowing that it will
+ * be deleted later during a transaction that deletes one reference and then
+ * creates a new conflicting reference. For example a rename from m to m/m.
  */
 static int is_refname_available(const char *refname, const char *oldrefname,
-				struct ref_dir *dir)
+				struct ref_dir *dir,
+				const char **skip, int skipnum)
 {
 	struct name_conflict_cb data;
 	data.refname = refname;
 	data.oldrefname = oldrefname;
 	data.conflicting_refname = NULL;
+	data.skip = skip;
+	data.skipnum = skipnum;
 
 	sort_ref_dir(dir);
 	if (do_for_each_entry_in_dir(dir, 0, name_conflict_fn, &data)) {
@@ -2032,7 +2046,8 @@ int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
 
 static struct ref_lock *lock_ref_sha1_basic(const char *refname,
 					    const unsigned char *old_sha1,
-					    int flags, int *type_p)
+					    int flags, int *type_p,
+					    const char **skip, int skipnum)
 {
 	char *ref_file;
 	const char *orig_refname = refname;
@@ -2079,7 +2094,9 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
 	 * name is a proper prefix of our refname.
 	 */
 	if (missing &&
-	     !is_refname_available(refname, NULL, get_packed_refs(&ref_cache))) {
+	     !is_refname_available(refname, NULL,
+				   get_packed_refs(&ref_cache),
+				   skip, skipnum)) {
 		last_errno = ENOTDIR;
 		goto error_return;
 	}
@@ -2137,7 +2154,7 @@ struct ref_lock *lock_any_ref_for_update(const char *refname,
 					 const unsigned char *old_sha1,
 					 int flags, int *type_p)
 {
-	return lock_ref_sha1_basic(refname, old_sha1, flags, type_p);
+	return lock_ref_sha1_basic(refname, old_sha1, flags, type_p, NULL, 0);
 }
 
 /*
@@ -2576,6 +2593,9 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
 	int log = !lstat(git_path("logs/%s", oldrefname), &loginfo);
 	const char *symref = NULL;
 
+	if (!strcmp(oldrefname, newrefname))
+		return 0;
+
 	if (log && S_ISLNK(loginfo.st_mode))
 		return error("reflog for %s is a symlink", oldrefname);
 
@@ -2586,10 +2606,12 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
 	if (!symref)
 		return error("refname %s not found", oldrefname);
 
-	if (!is_refname_available(newrefname, oldrefname, get_packed_refs(&ref_cache)))
+	if (!is_refname_available(newrefname, oldrefname,
+				  get_packed_refs(&ref_cache), NULL, 0))
 		return 1;
 
-	if (!is_refname_available(newrefname, oldrefname, get_loose_refs(&ref_cache)))
+	if (!is_refname_available(newrefname, oldrefname,
+				  get_loose_refs(&ref_cache), NULL, 0))
 		return 1;
 
 	if (log && rename(git_path("logs/%s", oldrefname), git_path(TMP_RENAMED_LOG)))
@@ -2622,7 +2644,7 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
 
 	logmoved = log;
 
-	lock = lock_ref_sha1_basic(newrefname, NULL, 0, NULL);
+	lock = lock_ref_sha1_basic(newrefname, NULL, 0, NULL, NULL, 0);
 	if (!lock) {
 		error("unable to lock %s for update", newrefname);
 		goto rollback;
@@ -2637,7 +2659,7 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
 	return 0;
 
  rollback:
-	lock = lock_ref_sha1_basic(oldrefname, NULL, 0, NULL);
+	lock = lock_ref_sha1_basic(oldrefname, NULL, 0, NULL, NULL, 0);
 	if (!lock) {
 		error("unable to lock %s for rollback", oldrefname);
 		goto rollbacklog;
@@ -3483,7 +3505,8 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 						    update->old_sha1 :
 						    NULL),
 						   update->flags,
-						   &update->type);
+						   &update->type,
+						   delnames, delnum);
 		if (!update->lock) {
 			if (err)
 				strbuf_addf(err ,"Cannot lock the ref '%s'.",
-- 
2.0.0.rc1.351.g4d2c8e4