Add support cd - got to prev directory

[kirillsalykin]

closes #166

This PR add support for cd -.

Implementation based on https://pubs.opengroup.org/onlinepubs/9699919799/utilities/cd.html.

In case if $OLDPWD is not set up - ~ used.
iTerm2 also uses same approach (with ~ as default), but builtin terminal doesn't.
(I am on mac os)

For me iTerm2 behavior feels more natural, but maybe you have other thoughts?

Thanks.

[dundalek]

Very cool 👍 I have one question as inline comment.

[dundalek]

Do we need this or is it left over from debugging?

[kirillsalykin]

We do need this.
According to the docs cd - should behave as cd $OLDPWD && pwd (besides settings env) - thus we need to print pwd (maybe in a different way tho).
(https://pubs.opengroup.org/onlinepubs/9699919799/utilities/cd.html
found here https://unix.stackexchange.com/questions/330876/difference-between-cd-and-cd)

Also, it seems a bit tricky how it can be tested (pwd output)
Should stdout be mocked for each env?

Please advice how you think it can be tested.

Thanks.

[dundalek]

I see, that's a good point. Traditional shells print to stdout, but I think we could try to just return the new PWD value instead of env/success. It will still get printed out when used on the command line. And it should be easier to test.

[kirillsalykin]

hey @dundalek ,

returning PWD indeed prints it, but it is printed via prn thus string is quoted, like this: "/Users/kirill.salykin/projects/closh". (which is not the way how other shells do this)

This is seems done by rebel.

What do you think?

Thanks.

[kirillsalykin]

It may be fixed with something like this:

(defn repl-print
  [& args]
  (if (string? (first args))
    (println (first args))
    (when-not (or (nil? (first args))
                  (identical? (first args) env/success)
                  (process? (first args)))
      (apply syntax-highlight-prn args))))

Shall I go for this?

[dundalek]

I think I kinda like it that it is printed as a string, feels more structured. I think it is good for now, if it causes any trouble in the future we can change it to println.