Prevent improper files (like /dev/random) from being used as file arguments

[TiredTumblrina]

As per the suggestions in #10726 this pull request changes the argument parsing to only add a PathBuf to args.files if it is either a file or a symlink. This has been tested on the scenarios provided in the issue and simply opens an empty buffer as if no argument was provided in those cases. (instead of freezing)

[pascalkuthe]

I don't think the arg parsing is the right place to do this. We should fundamentally disallow opening non-files so it's consistent with :open/:vsplit and any other way a user would open a path

[TiredTumblrina]

That is a good point, I'll see if I can get this to work in a more interoperable way and will amend the PR

[TiredTumblrina]

By making changes to the Document::open method I have the :open command working as expected, however when I revert the prior changes to argument parsing the application errors out ungracefully:

> hx /dev/random
Error: unable to create new application

Caused by:
    0: open '/dev/random'
    1: Path argument /dev/random should lead is not a regular file or a symlink.

In this case, maybe it would be better to keep both checks so that the application does not crash when it gets an invalid input?

[kirawi]

You probably need to handle that error and just create an empty scratch buffer if the file can't open.

[TiredTumblrina]

done, thank you all for the suggestions and advice!