Deterministic file type detection

[pyfisch]

Description of the problem or steps to reproduce

#2163 showed that the filetype detection is not deterministic: if multiple detect rules match a given filename a random filetype is chosen that varies between executions. At minimum each invocation of micro should detect the same file type. An additional measure may be to warn or error if the file is detected as multiple types.

I think it would be preferable that if both a built-in detect rule and a user provided detect rule exist only the latter is used. This would allow users to overwrite detection rules without recompiling micro.

Specifications

Version: 2.0.5-dev.279
Commit hash: c98239d
Compiled on July 21, 2021

Commit hash: 6e1fe5b
OS: Linux
Terminal: alacritty

[zyedidia]

On this front I think we should focus on changing micro to use this package: https://github.com/zyedidia/ftdetect, and implementing any additional functionality there. That package already supports deterministic filetype detection.

Currently it is possible to override the detection via globs in the settings file, but a more robust method could be useful.

[MaximilianEmel]

This really needs to be fixed. I stopped using this editor a year ago because of this issue.