feat: set the HOME environment variable before invoking a command

[etorreborre]

This should solve #26 where the global .gitignore file cannot be found.

[chshersh]

Looks great! Thanks for your contribution 💯

Two things left:

• Could you add a changelog
• The HOME code here can be simplified

  • zbg/lib/git.ml

    Lines 22 to 27 in 311e035

    	let home_dir = Unix.getenv "HOME" in
    	let login =
    	Process.proc_stdout
    	@@ Printf.sprintf "HOME=%s git config user.login" home_dir
    	in
    	if String.is_empty login then None else Some login

[etorreborre]

• Could you add a changelog
• The HOME code here can be simplified -> Ah, yes of course!

[chshersh]

Awesome, looks great!

[etorreborre]

BTW I forgot to mention that this PR indeed solves #26
Before:

After:

[chshersh]

Thanks again!