refs.c: allow deleting refs with a broken sha1rs/ref-transaction-reflog

Add back support to make it possible to delete refs that have a broken
sha1.

Add new internal flags REF_ALLOW_BROKEN and RESOLVE_REF_ALLOW_BAD_SHA1
to pass intent from branch.c that we are willing to allow
resolve_ref_unsafe and lock_ref_sha1_basic to allow broken refs.
Since these refs can not actually be resolved to a sha1, they instead resolve
to null_sha1 when these flags are used.

For example, the ref:

   echo "Broken ref" > .git/refs/heads/foo-broken-1

can now be deleted using git branch -d foo-broken-1

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/cache.h b/cache.h
index 0501f7dca8..b76cdb2cc8 100644
--- a/cache.h
+++ b/cache.h
@@ -1000,10 +1000,17 @@ extern int read_ref(const char *refname, unsigned char *sha1);
  * resolved. The function returns NULL for such ref names.
  * Caps and underscores refers to the special refs, such as HEAD,
  * FETCH_HEAD and friends, that all live outside of the refs/ directory.
+ *
+ * RESOLVE_REF_ALLOW_BAD_SHA1 when this flag is set and the ref contains
+ * an invalid sha1, resolve_ref_unsafe will clear the sha1 argument,
+ * set the REF_ISBROKEN flag and return the refname.
+ * This allows using resolve_ref_unsafe to check for existence of such
+ * broken refs.
  */
 #define RESOLVE_REF_READING 0x01
 #define RESOLVE_REF_NO_RECURSE 0x02
 #define RESOLVE_REF_ALLOW_BAD_NAME 0x04
+#define RESOLVE_REF_ALLOW_BAD_SHA1 0x08
 extern const char *resolve_ref_unsafe(const char *ref, int resolve_flags, unsigned char *sha1, int *flags);
 extern char *resolve_refdup(const char *ref, int resolve_flags, unsigned char *sha1, int *flags);