cvs: build with openssh

[joshuakb2]

This change adds openssh as a dependency of cvs and builds cvs with a fully qualified path to the ssh binary it should use. Without openssh, cvs tries to use rsh to access remote repositories, so other modern distributions (Ubuntu for example) specify something like --with-rsh=/usr/bin/ssh when configuring cvs.

I tried to get this change introduced a while back in #347374, but it must've gotten lost in the weeds. I've been using a custom overlay all this time so I never noticed the standard cvs package still can't use ssh.

Although this pull request has the same end goal as the previous one, I think this one is a much better approach.

Things done

• Built on platform:
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• Tested, as applicable:
  • NixOS tests in nixos/tests.
  • Package tests at passthru.tests.
  • Tests in lib/tests or pkgs/test for functions and "core" functionality.
• Ran nixpkgs-review on this PR. See nixpkgs-review usage.
• Tested basic functionality of all binary files, usually in ./result/bin/.
• Nixpkgs Release Notes
  • Package update: when the change is major or breaking.
• NixOS Release Notes
  • Module addition: when adding a new NixOS module.
  • Module update: when the change is significant.
• Fits CONTRIBUTING.md, pkgs/README.md, maintainers/README.md and other READMEs.

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[tomfitzhenry]

other modern distributions (Ubuntu for example) specify something like --with-rsh=/usr/bin/ssh when configuring cvs

Do you have a link for this? That'll make it easier to have confidence this'll work.

[joshuakb2]

Here's the diff debian applies to the latest version of their cvs package: http://deb.debian.org/debian/pool/main/c/cvs/cvs_1.12.13+real-30.diff.gz

You can see that they add --with-rsh=/usr/bin/ssh, and Ubuntu does the same but I had a harder time accessing ubuntu package sources than debian's.

I checked what Arch does with their cvs package, and they actually don't add this configure flag. Then I checked Fedora, and they do set the default to ssh. So basically the distros I've used before configure with ssh, but some modern and popular distros do not.

Maybe it should be left as is, then. At runtime cvs will use whatever is specified in the CVS_RSH environment variable if it's present. I just expected it to work like it had before for me out of the box, but maybe some people actually do still use it with rsh and this change would screw them up. I've just never done so.

[joshuakb2]

Considering that arch doesn't build with openssh and that it's relatively easy to get cvs to use openssh by changing one environment variable, I'm closing this pull request.