diff options
Diffstat (limited to 'refs/files-backend.c')
| -rw-r--r-- | refs/files-backend.c | 40 |
1 files changed, 38 insertions, 2 deletions
diff --git a/refs/files-backend.c b/refs/files-backend.c index bf6f89b1d1..ba018b0984 100644 --- a/refs/files-backend.c +++ b/refs/files-backend.c @@ -68,6 +68,12 @@ */ #define REF_DELETED_RMDIR (1 << 9) +/* + * Used to indicate that the reflog-only update has been created via + * `split_head_update()`. + */ +#define REF_LOG_VIA_SPLIT (1 << 14) + struct ref_lock { char *ref_name; struct lock_file lk; @@ -2420,9 +2426,10 @@ static enum ref_transaction_error split_head_update(struct ref_update *update, new_update = ref_transaction_add_update( transaction, "HEAD", - update->flags | REF_LOG_ONLY | REF_NO_DEREF, + update->flags | REF_LOG_ONLY | REF_NO_DEREF | REF_LOG_VIA_SPLIT, &update->new_oid, &update->old_oid, NULL, NULL, update->committer_info, update->msg); + new_update->parent_update = update; /* * Add "HEAD". This insertion is O(N) in the transaction @@ -2600,7 +2607,36 @@ static enum ref_transaction_error lock_ref_for_update(struct files_ref_store *re update->backend_data = lock; - if (update->type & REF_ISSYMREF) { + if (update->flags & REF_LOG_VIA_SPLIT) { + struct ref_lock *parent_lock; + + if (!update->parent_update) + BUG("split update without a parent"); + + parent_lock = update->parent_update->backend_data; + + /* + * Check that "HEAD" didn't racily change since we have looked + * it up. If it did we must refuse to write the reflog entry. + * + * Note that this does not catch all races: if "HEAD" was + * racily changed to point to one of the refs part of the + * transaction then we would miss writing the split reflog + * entry for "HEAD". + */ + if (!(update->type & REF_ISSYMREF) || + strcmp(update->parent_update->refname, referent.buf)) { + strbuf_addstr(err, "HEAD has been racily updated"); + ret = REF_TRANSACTION_ERROR_GENERIC; + goto out; + } + + if (update->flags & REF_HAVE_OLD) { + oidcpy(&lock->old_oid, &update->old_oid); + } else { + oidcpy(&lock->old_oid, &parent_lock->old_oid); + } + } else if (update->type & REF_ISSYMREF) { if (update->flags & REF_NO_DEREF) { /* * We won't be reading the referent as part of |