Support SSH variant for NonStop SSH

[rsbeckerca]

There should be native support in git for NonStop SSH.

Describe the solution you'd like
git supports the concept of SSH variants through the core.sshVariant configuration variable in .gitconfig. There should be a new entry called nonstopssh or something acceptable to the git team. This will build a proper command to run /G/system/zssh/sshoss. The processing should account for the port and SSH2 process.

The modifications should all be contained in connect.c starting here:

git/connect.c

Line 1087 in 32a64f5

enum ssh_variant {

The following parameters need to get in somehow:

-p port is pretty much handled.
-Q to quiet. This should be passed in as an environment variable either to enable or disable by default.
-Z to suppress the header. This is really important as it will cause dialog problems in older SSH SPRs.
-S process if getenv("SSH2_PROCESS_NAME") is in the environment, this must be added.

Modifications should be pretty trivial, except for possible handling of =SSH2^PROCESS^NAME, for which I have some code that can be inserted.

Alternatives
Currently, the user needs a wrapper that runs SSHOSS. This is usually sufficient, but people are not happy with it.

Additional Issues
The DEFINE =SSH2^PROCESS^NAME may be used by SSHOSS if in the environment. This is an unknown right now (please discuss).

Note: the contribution of any fixes to our code must go through the git workflow, not added as a Pull Request on GitHub.

[rsbeckerca]

I have pushed a candidate implementation that does not take into account =SSH2^PROCESS^NAME. Documentation has not yet been done but will follow after this works. Please review: @Jojo-Schmitz @xidbhonaker @the4amfriend

[Jojo-Schmitz]

Seems I can't formally approve, but yes, this looks good to me. Question is whether the git team accepts it.

[rsbeckerca]

@Jojo-Schmitz What do you think about the =SSH2_PROCESS_NAME define question?

[Jojo-Schmitz]

No idea. I guess getting that past the git team might get difficult, as it is very foreign to anyone outside the NonStop world

[rsbeckerca]

No idea. I guess getting that past the git team might get difficult, as it is very foreign to anyone outside the NonStop world

That's a point. @xidbhonaker ?

[xidbhonaker]

The change looks reasonable, and your suggested changes appear to be sound. As for use of the Define, you definitely know the git team better than I do... but it seems to be the easiest for the end users. As long as the calls to access the DEFINE are encapsulated and don't break builds on other platforms, what would their objection(s) likely be?

[rsbeckerca]

From the SSH manual:

By setting an environment variable SSH2_PROCESS_NAME in the OSS shell specifying the SSH2 process, the client should use.

So I think I have to support this. Ah well. Will do it and try to explain.

[Jojo-Schmitz]

I'd go for the environment variable. Much more UNIXy

[Jojo-Schmitz]

What is taken if define and param/env-var are set?

[rsbeckerca]

I think we are fine without it. If the user specifies the DEFINE outside of git, it still gets passed in, at least if we turn defmode on.

What is taken if define and param/env-var are set?

By git convention, the env-var always overrides everything.

[xidbhonaker]

That seems to be the best strategy

[rsbeckerca]

That seems to be the best strategy

Thanks. I've got the Documentation done. Going to think about how to test this on platforms that don't have sshoss.

[Jojo-Schmitz]

Temporarily move it aside?