Allow passing a list of refs to skip 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 and 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 <sahlb...@google.com>
---
 refs.c | 41 ++++++++++++++++++++++++++---------------
 1 file changed, 26 insertions(+), 15 deletions(-)

diff --git a/refs.c b/refs.c
index d3fedbb..a115478 100644
--- a/refs.c
+++ b/refs.c
@@ -801,15 +801,18 @@ static int names_conflict(const char *refname1, const 
char *refname2)
 
 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;
-       if (data->oldrefname && !strcmp(data->oldrefname, entry->name))
-               return 0;
+       int i;
+       for (i = 0; i < data->skipnum; i++)
+               if (!strcmp(entry->name, data->skip[i]))
+                       return 0;
        if (names_conflict(data->refname, entry->name)) {
                data->conflicting_refname = entry->name;
                return 1;
@@ -822,15 +825,18 @@ 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.
  */
-static int is_refname_available(const char *refname, const char *oldrefname,
-                               struct ref_dir *dir)
+static int is_refname_available(const char *refname,
+                               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)) {
@@ -2077,7 +2083,8 @@ int dwim_log(const char *str, int len, unsigned char 
*sha1, char **log)
 /* 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)
+                                           int flags, int *type_p,
+                                           const char **skip, int skipnum)
 {
        char *ref_file;
        const char *orig_refname = refname;
@@ -2126,7 +2133,8 @@ 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, get_packed_refs(&ref_cache),
+                                  skip, skipnum)) {
                last_errno = ENOTDIR;
                goto error_return;
        }
@@ -2184,7 +2192,7 @@ 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);
 }
 
 /*
@@ -2654,10 +2662,12 @@ 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, get_packed_refs(&ref_cache),
+                                 &oldrefname, 1))
                return 1;
 
-       if (!is_refname_available(newrefname, oldrefname, 
get_loose_refs(&ref_cache)))
+       if (!is_refname_available(newrefname, get_loose_refs(&ref_cache),
+                                 &oldrefname, 1))
                return 1;
 
        if (log && rename(git_path("logs/%s", oldrefname), 
git_path(TMP_RENAMED_LOG)))
@@ -2687,7 +2697,7 @@ 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;
@@ -2702,7 +2712,7 @@ 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;
@@ -3580,7 +3590,8 @@ 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'.",
-- 
2.0.1.527.gc6b782e

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