internal/cmd: git_wrapper: add git stash push to wrapped subcommands

[christoph-heiss]

Pretty much as it says on the tin.

git stash push (optionally) also takes path(s) for its arguments, so translate them.

[christoph-heiss]

@mroth Mind taking a look?

[mroth]

@christoph-heiss sorry for the delay, let me take a look.

[mroth]

Nice, well-scoped change — translating only stash push is exactly right, since for pop/apply/drop/show a number is a stash index (git stash pop 1), not a file number, so expanding it would be actively wrong.

One non-blocking suggestion: that reasoning is the whole point of the push-only branch, but it's currently implicit. A one-line comment would help a future reader (and stop someone from "helpfully" widening the case):

In git_wrapper.sh:

    stash)
      # Only `stash push` takes pathspecs; for pop/apply/drop/show a number is a
      # stash index, not a file number, so pass those through untranslated.
      case ${2-:} in
        push)
          scmpuff exec --relative -- "$SCMPUFF_GIT_CMD" "$@";;
        *)
          "$SCMPUFF_GIT_CMD" "$@";;
      esac
      ;;

…and the equivalent above the switch $argv[2] in git_wrapper.fish.

Otherwise this looks good. I pushed a couple of integration tests to the branch to lock in the behavior across bash/zsh/fish — one for git stash push <n> expanding to the right path, and one verifying bare git stash / git stash pop pass through unchanged (which also confirms the empty-$argv[2] path is fine in fish). Take a look and let me know what you think.

(Review drafted by by Claude Opus but manually reviewed by @mroth )