.gitmodules containing SSH clone URLs should fall back to HTTPS when SSH key is not valid/existent

The title pretty much says it all. Lack of this feature (or presence of this bug [depending on your perspective]) is a major PITA.

--Jonathan

Am 29.05.2014 04:07, schrieb Jonathan Leonard:

But you do not give much information about your special use case. I assume you have submodule repositories for which some developers have a valid ssh key and others don't (maybe because they should only have read access via https)?

If that is the case you might want to look into access control tools like gitolite.

But why is https special? Why not fall back to the git protocol? Or http? (And no: I'm not serious here ;-)

After the first failed clone of the submodule at via SSH the developer could also just do a

   git config submodule.<name>.url https://host/repo

and override the URL from .gitmodules.

But maybe I misunderstood why you want to have a fall back?

Jens Lehmann <Jens.Lehmann@web.de> writes:

Perhaps "git grep insteadOf Documentation/" is all that is needed?

Precisely. Specifically this is for a collection (17 or more) of GitHub-hosted projects which are maintained by only a couple of people (who have the ability to directly push via git:// or ssh://). Everyone else (including deployments and ordinary users) who clones the repo should be able to just grab the code via HTTPS and have it work.

We are using GitHub.

HTTPS isn't special except in that it is the least privileged transport type (and thus should be the last resort). Whether to fallback to git:// from ssh:// or vice versa is inconsequential to this request.

Yes, this would work. But it would be a painful manual step which we would not want to force on ordinary users (and would not want to experience ourselves either).

It should be noted that this is only really a problem as the other
options GitHub gives us are also equally (or more) painful:
a) - a unique deploy key per machine and project. (which at current
would be 17 * 3 keys all manually maintained via clicking through a
GUI [unless we wanted to automate via GitHub API (which is also a
non-trivial amount of work)]).
- or -
b) - a fake 'team' with read-only access with a single fake GitHub
account as member thereof.

I imagine this feature would be convenient for non-GitHub scenarios as well though.

--Jonathan

On Thu, May 29, 2014 at 04:12:38PM -0700, Jonathan Leonard wrote:

That's not quite true. git:// is the least privileged transport, as it always anonymous and read-only (there ways to allow insecure pushes over it, but GitHub does not enable them). Https is actually the most flexible protocol, in that the same URL works of the box for both logged-in and anonymous users (the latter assuming the repo is publicly available). The server only prompts for credentials if necessary.

For that reason, it's a good choice for things like submodule URLs baked into .gitmodules files.

The reasons not to are:

  1. It isn't _quite_ as efficient or robust as the regular git
     protocol, though in practice it's generally not a big deal.

  2. Pushers may prefer to authenticate with ssh keys (e.g., because
     they run ssh agent). I hope with modern credential helpers that
     logging in via http should not be a pain, either, though.

Using insteadOf of in your global ~/.gitconfig would make this a one-liner per-user. So one option would be to reverse things. Put "https" URLs into the .gitmodules file, so most people have to do nothing, and then developers who really want to do git-over-ssh can do a one-time:

  git config --global url.git@github.com:.insteadOf https://github.com/

-Peff

On Fri, May 30, 2014 at 11:12 AM, Jonathan Leonard <johanatan@gmail.com> wrote:

The problem is that a ssh:// url can't necessarily be transformed into a correct https:// or git:// with a simple sed 's/ssh/https/' chances are other parts of the URL will need changing. Which quickly becomes non-trivial.

One solution that we use at work is to use relative paths (e.g. ../code/mod1.git) in .gitmodules (assuming the submodules are all part of the same project). That way if you clone the superproject over https:// all the submodules use that too. This works well for us using local mirrors across multiple sites _and_ different protocols.

Another option would be to have a policy of storing the most permissive transport in .gitmodules which makes it easy for users and puts the special config requirements on the maintainers.

Both of these are obviously solutions you need to convince the maintainer(s) of the superproject to implement.

Perhaps what git could do is allow multiple urls for a submodule and at git submodule init time try them in order until the fetch is successful. Or provide a mechanism to map transports, arguably this is the url.<foo>.insteadOf mechanisim that has already been suggested.