[skara] RFR: Make "git debug mlrules" tolerate missing files, and clarify help

[Robin Westberg]

On Wed, 24 Mar 2021 15:29:15 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

> The "mlrules" debug command crashed if given non-existing files.
> 
> Also clarify the difference between files to test for, and path to the config file.

Looks good!

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Marked as reviewed by rwestberg (Reviewer).

PR: https://git.openjdk.java.net/skara/pull/1093