Fix powershell shebang, closes #825

[sigoden]

No description provided.

[casey]

Thanks for the PR!

Can you add a test that this works on windows? Check out the tests directory. You can put it in a new module, maybe tests/shebang.rs.

Also, what if the users writes:

foo:
  #!powershell

…without .exe. If that works, we should check for that too. Also, do we need to add a suffix for pwsh.exe?

Even though this is windows specific, let's do it on every platform. The less platform-specific code there is the better, and it won't hurt to add a .ps1 suffix on macOS and Linux.

[casey]

Since this isn't platform specific, we can just inline it:

Suggested change

	let suffix = Platform::get_script_file_suffix(interpreter);
	let suffix = if command.ends_with("powershell")
	|| command.ends_with("powershell.exe")
	{
	".ps1"
	} else {
	""
	};

[casey]

I made an additional suggestion. We can move the suffix function out of Platform because it's not platform specific anymore. Also, CI is catching some unformatted code. You can do cargo +nightly fmt --all to format the code. (You'll need nightly rust, since there's some additional rustfmt options that I enable that aren't available on stable.)

[casey]

Thanks again for the PR! Let me know if you'd like me to cut a release of Just that contains the new code.