On Thu, Sep 13, 2012 at 11:10:26PM -0700, Junio C Hamano wrote:
> I do not think it is a good idea to allow such a helper to claim that
> it supports "fetch" capability, for at least two reasons:
>
> * Being able to "list" is essential for "fetch" based helpers.
> think, far from "arbitrary".
> ...
Oh, I don't mean to change the semantics of the list command at all.
What I thought seemed arbitrary was limiting the *fetch* command to refs
with pre-known sha1s. Any list-time optimization in place or possible
for such refs wouldn't be affected.
(In light of this, specifying a new sha1 for a ref which already had one
in the list should probably be an error rather than a warning. I'll
update this in the next version and make it clear that a "ref" message
must only be issued for refs reported without a sha1.)
> * Existing versions of "git" that can drive remote helpers that
> claim to have "fetch" capability are not prepared to accept an
> unknown "refs" protocol message from the helper, so a helper
> written for your new semantics of "fetch" capability will not
> work with them.
> ...
I see. I didn't realize that new helper + old Git client is a supported
combination. Still, hear me out.
1. A new helper must only send a "ref" message when git asks for a ref
without a known sha1.
2. Asking for a ref without a known sha1 is unsupported, according to
git-remote-helpers.txt: "Only objects which were reported in the ref
list with a sha1 may be fetched [with fetch]."
3. Furthermore, asking for a ref without a known sha1 *already* breaks
in existing versions of git with current handlers:
$ git fetch testfetch::../git1 foo
fatal: bad object 0000000000000000000000000000000000000000
error: testfetch::../git1 did not send all necessary objects
Compare - existing version of git, with a new handler:
$ git fetch testref::../git1 foo
warning: testref unexpectedly said: 'ref 0f31<snip> refs/heads/foo'
fatal: bad object 0000000000000000000000000000000000000000
error: testref::../git1 did not send all necessary objects
So the proposed change doesn't break anything that isn't already broken.
:)
That said, if you're still not sold, a new capability is fine. Though I
think it can be done without it, I'm certainly not opposed to adding
one.
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