All basic commands should accept file names or a flag --all

[StephanLoor]

My idea is to fix two "issues" at the same time:

1. At present, diff and clean can only be applied to all files at once, i.e. they cannot be applied to individual files.
2. There are two separate commands fix and fix_all, even though the latter really just applies the former to every .rej file present.

My proposal would be to do the following:

1. Add an optional flag --all to the fix command, and make the input variable rej_file_path optional (with default value ''). Typer can be used to implement this.
2. If the flag --all passed, run what is currently fix_all.
3. Remove fix_all as a separate command.
4. If --all is not passed, check if rej_file_path == ''. If this is the case, then raise an error. Otherwise, apply the current fix command.
5. Apply the same logic to diff and clean.

@MarkusSagen if you like these ideas, I can have a go at implementing them myself 😄

[MarkusSagen]

💯 Great suggestion! It was not the ideal flow for implementing this before and I think the proposed change is what it should have been from the beginning

@StephanLoor, if you would like to take a stab at it, that would be much appreciated 😃

[StephanLoor]

Closed as completed in #6

[MarkusSagen]

Included in the 0.2.0 release