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delete_ref(): use the usual convention for old_sha1

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The ref_transaction_update() family of functions use the following
convention for their old_sha1 parameters:

* old_sha1 == NULL: Don't check the old value at all.
* is_null_sha1(old_sha1): Ensure that the reference didn't exist
  before the transaction.
* otherwise: Ensure that the reference had the specified value before
  the transaction.

delete_ref() had a different convention, namely treating
is_null_sha1(old_sha1) as "don't care". Change it to adhere to the
standard convention to reduce the scope for confusion.

Please note that it is now a bug to pass old_sha1=NULL_SHA1 to
delete_ref() (because it doesn't make sense to delete a reference that
you already know doesn't exist). This is consistent with the behavior
of ref_transaction_delete().

Most of the callers of delete_ref() never pass old_sha1=NULL_SHA1 to
delete_ref(), and are therefore unaffected by this change. The
two exceptions are:

* The call in cmd_update_ref(), which passed NULL_SHA1 if the old
  value passed in on the command line was 0{40} or the empty string.
  Change that caller to pass NULL in those cases.

  Arguably, it should be an error to call "update-ref -d" with the old
  value set to "does not exist", just as it is for the `--stdin`
  command "delete". But since this usage was accepted until now,
  continue to accept it.

* The call in delete_branches(), which could pass NULL_SHA1 if
  deleting a broken or symbolic ref. Change it to pass NULL in these
  cases.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Michael Haggerty
2015-06-22 16:03:10 +02:00
committed by Junio C Hamano
parent e2991c8048
commit 1c03c4d347
4 changed files with 14 additions and 15 deletions
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8
builtin/update-ref.c
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@ -422,7 +422,13 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
if (no_deref)
flags = REF_NODEREF;
if (delete)
return delete_ref(refname, oldval ? oldsha1 : NULL, flags);
/*
* For purposes of backwards compatibility, we treat
* NULL_SHA1 as "don't care" here:
*/
return delete_ref(refname,
(oldval && !is_null_sha1(oldsha1)) ? oldsha1 : NULL,
flags);
else
return update_ref(msg, refname, sha1, oldval ? oldsha1 : NULL,
flags, UPDATE_REFS_DIE_ON_ERR);