Pass the try_from_str functions a &str instead of a &String.

[m-ou-se]

In most cases this doesn't matter, as &String is coerced to a &str, but
this fails for generic functions like CString::new.

The added test failed to compile before this change.

[TeXitoi]

Thanks for your contribution!

Some questions:

• Don't we have the same problem with from_str, from_ostr and try_from_os_str
• Don't we need to do this fix at some other places to be safe

Please also add a line in the CHANGELOG.md

[m-ou-se]

It was only a problem in the validation step, not in the conversion step. So the non-try_ variants are fine.

try_from_os_str is also fine, because Clap's validator_os gives an &OsStr to the function. Only Clap's validator is a bit weird, as it gives a String (by value).

[TeXitoi]

Thanks.

[TeXitoi]

v0.3.5 published