Re: upstreaming https://github.com/cgwalters/git-evtag ?

From: Stefan Beller <sbeller@google.com>
Date: Jan 8, 2018, 20:49 UTC
Message-ID: <CAGZ79kZ8AXezcX1_5WJsUJMHiHCzj2B=Uj8+4K3VF+cC6mTCqA@mail.gmail.com>
In-Reply-To: <20180108204029.m42qyezojak4kohh@LykOS.localdomain>

On Mon, Jan 8, 2018 at 12:40 PM, Santiago Torres <santiago@nyu.edu> wrote:

Show 9 quoted lines

> Hi,
>
> I personally like the idea of git-evtags, but I feel that they could be
> made so that push certificates (and being hash-algorithm agnostic)
> should provide the same functionality with less code.
>
> To me, a git evtag is basically a signed tag + a data structure similar
> to a push certificate embedded in it. I wonder if, with the current
> tooling in git, this could be done as a custom command...

In that case, why not migrate Git to a new hash function instead of adding a very niche fixup?

See Documentation/technical/hash-function-transition.txt for how to do it.

Personally I'd dislike to include ev-tags as it might send a signal of "papering over sha1 issues instead of fixing it".

push certificates are somewhat underdocumented, see the
git-push man page, which contains
       --[no-]signed, --signed=(true|false|if-asked)
           GPG-sign the push request to update refs on the
           receiving side, to allow it to be checked by the
           hooks and/or be logged. If false or --no-signed, no
           signing will be attempted. If true or --signed, the
           push will fail if the server does not support signed
           pushes. If set to if-asked, sign if and only if the
           server supports signed pushes. The push will also
           fail if the actual call to gpg --sign fails. See git-
           receive-pack(1) for the details on the receiving end.

Going to receive-pack(1), there is an excerpt:

      When accepting a signed push (see git-push(1)), the
       signed push certificate is stored in a blob and an
       environment variable GIT_PUSH_CERT can be consulted for
       its object name. See the description of post-receive hook
       for an example. In addition, the certificate is verified
       using GPG and the result is exported with the following
       environment variables:
...

Stefan