ssh: add addKeysToAgent option

[lockejan]

Description

add addKeysToAgent option to ssh module

Checklist

• Change is backwards compatible.

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• Code tested through nix-shell --pure tests -A run.all.

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[stale]

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[lockejan]

My concerns persist, but I've changed the PR as suggested. I've rebased and ran all tests again. I leave the final decision to @rycee . Feel free to close or merge.

[sumnerevans]

Probably needs a rebase to get the tests passing.

[lockejan]

Probably needs a rebase to get the tests passing.

Maybe you are right. I rebased and ran the tests again locally, this time against the flake inputs nix develop --ignore-environment .#all.
No errors whatsoever.
Should be fine now.

[stale]

Thank you for your contribution! I marked this pull request as stale due to inactivity. Please read the relevant sections below before commenting.

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[lockejan]

@sumnerevans

[stale]

Thank you for your contribution! I marked this pull request as stale due to inactivity. Please read the relevant sections below before commenting.

If you are the original author of the PR

• GitHub sometimes doesn't notify people who commented / reviewed a PR previously when you (force) push commits. If you have addressed the reviews you can officially ask for a review from those who commented to you or anyone else.
• If it is unfinished but you plan to finish it, please mark it as a draft.
• If you don't expect to work on it any time soon, please consider closing it with a short comment encouraging someone else to pick up your work.
• To get things rolling again, rebase the PR against the target branch and address valid comments.

If you are not the original author of the PR

• If you want to pick up the work on this PR, please create a new PR and indicate that it supercedes and closes this PR.

[rycee]

Sorry about the delay! Finally round to merging this 🙂

[sersorrel]

Change is backwards compatible.

unfortunately this change inscrutably breaks behaviour for anyone who set programs.ssh.extraConfig to "AddKeysToAgent yes" already, since per ssh_config(5) "for each parameter, the first obtained value will be used" and the new programs.ssh.addKeysToAgent inserts its AddKeysToAgent line before extraConfig.