Improve shell variant detection for shfmt

[rolandmas]

This adds a suffix to the filename passed to shfmt so it can use the default settings stored in .editorconfig even for shell scripts without an extension.

[lassik]

Thanks. A better approach is to always use -ln instead of using fake filenames.

[lassik]

I can write the code.

[lassik]

Wait, editorconfig. Isn't it supposed to be based on filename patterns only? So if you want to use editoconfig settings for foo, you have to write a [foo] section in the .editorconfig file?

[rolandmas]

Yes, correct. Which is why I needed to write a section for [.sh] and [.bash] in that file in order to save default settings for shfmt; and using -ln only doesn't cause shfmt to read these sections because it's based on filenames, hence the tweak in -filename.