Re: Can I fetch an arbitrary commit by sha1?

On Thu, Oct 02, 2014 at 10:22:50AM -0400, Dan Johnson wrote:

quoted

quoted

git show af00f4c39bcc8dc29ed8f59a47066d5993c279e4

fatal: bad object af00f4c39bcc8dc29ed8f59a47066d5993c279e4

quoted

git fetch origin af00f4c39bcc8dc29ed8f59a47066d5993c279e4

error: no such remote ref af00f4c39bcc8dc29ed8f59a47066d5993c279e4

quoted

git fetch origin refs/foo/b1

remote: Counting objects: 3, done.
remote: Compressing objects: 100% (2/2), done.
remote: Total 3 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.
From https://github.com/chalstrick/dondalfi
 * branch            refs/foo/b1 -> FETCH_HEAD

quoted

git fetch origin af00f4c39bcc8dc29ed8f59a47066d5993c279e4

From https://github.com/chalstrick/dondalfi
 * branch            af00f4c39bcc8dc29ed8f59a47066d5993c279e4 -> FETCH_HEAD

My understanding is that you are allowed to ask for a SHA1, but most
git servers refuse the request. But if you already have the SHA
locally, then git doesn't neet to bother asking the server for it, so
there's no request to be refused.

That's right. It is the server which enforces the "you cannot fetch an
arbitrary sha1" rule.

But I think Christian is arguing that the client side should complain
that $sha1 is not a remote ref, and therefore not something we can
fetch.  This used to be the behavior until 6e7b66e (fetch: fetch objects
by their exact SHA-1 object names, 2013-01-29). The idea there is that
some refs may be kept "hidden" from the ref advertisement, but clients
who learn about the sha1 out-of-band may fetch the tips of hidden refs.

I'm not sure it is a feature that has been particularly well-used to
date, though.

-Peff