Re: [PATCH v6 0/8] push: update remote tags only with force

On Wed, Jan 16, 2013 at 9:11 PM, Jeff King [off-list ref] wrote:

quoted

is_forwardable() did solve a UI issue.  Previously all instances where
old is not reachable by new were assumed to be addressable with a
merge.  is_forwardable() attempted to determine if the concept of
forwarding made sense given the inputs.  For example, if old is a blob
it is useless to suggest merging it.

I think it makes sense to mark such a case as different from a regular
non-fast-forward (because "git pull" is not the right advice), but:

  1. is_forwardable should assume a missing object is a commit not to
     regress the common case; otherwise we do not show the pull advice
     when we probably should, and most of the time it is going to be a
     commit

Yes, obviously this was a bug, thus the use of "attempted" above.  It
would have been better to assume a missing 'old' was potentially
forwardable to present the user with the most helpful advice.

  2. When we know that we are not working with commits, I am not sure
     that "already exists" is the right advice to give for such a case.
     It is neither "this tag already exists, so we do not update it",
     nor is it strictly "cannot fast forward this commit", but rather
     something else.

But the reference already existing in the remote is a substantial
reason for not allowing the push in all of these cases.  You can break
this out further if you like to explain why the specific reference
shouldn't be moved on the remote, but this is even more complicated a
simple "is old reachable from new?" test.

Chris