refs/files: use correct error type when lock exists

When fetching references into a repository, if a lock for a particular
reference exists, then `lock_raw_ref()` throws:

    - REF_TRANSACTION_ERROR_CASE_CONFLICT: when there is a conflict
    because the transaction contains conflicting references while being
    on a case-insensitive filesystem.

    - REF_TRANSACTION_ERROR_GENERIC: for all other errors.

The latter causes the entire set of batched updates to fail, even in
case sensitive filessystems.

Instead, return a 'REF_TRANSACTION_ERROR_CREATE_EXISTS' error. This
allows batched updates to reject the individual update which conflicts
with the existing file, while updating the rest of the references.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 18 insertions, 3 deletions

diff --git a/refs/files-backend.c b/refs/files-backend.c
index 01df32904b..d1af5d6bc7 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -797,9 +797,24 @@ retry:
 			goto retry;
 		} else {
 			unable_to_lock_message(ref_file.buf, myerr, err);
-			if (myerr == EEXIST && ignore_case &&
-			    transaction_has_case_conflicting_update(transaction, update))
-				ret = REF_TRANSACTION_ERROR_CASE_CONFLICT;
+			if (myerr == EEXIST) {
+				if (ignore_case &&
+				    transaction_has_case_conflicting_update(transaction, update)) {
+					/*
+					 * In case-insensitive filesystems, ensure that conflicts within a
+					 * given transaction are handled. Pre-existing refs on a
+					 * case-insensitive system will be overridden without any issue.
+					 */
+					ret = REF_TRANSACTION_ERROR_CASE_CONFLICT;
+				} else {
+					/*
+					 * Pre-existing case-conflicting reference locks should also be
+					 * specially categorized to avoid failing all batched updates.
+					 */
+					ret = REF_TRANSACTION_ERROR_CREATE_EXISTS;
+				}
+			}
+
 			goto error_return;
 		}
 	}