`PROTONPATH` UMU-Proton codename missing

[RoGreat]

Discussed the issue here.

README states:

PROTONPATH designates the full path to a specific proton version. Alternatively you can use value "GE-Proton" to auto-download and use the latest GE-Proton build. Defaults to UMU-Proton. (UMU-Proton is the latest stable version of Valve's proton tool with UMU compatibility added)

The docs also states that by default it uses UMU-Proton. Whenever I do that though, there's an error:

ValueError: Failed to match 'UMU-Proton' with a container runtime

It does work however when I use the UMU-Latest codename. I think the intent is that using PROTONPATH at all would assume that you are not using UMU-Proton. With some applications though, that variable is always present. Having it be empty results in an error as well which is not ideal.

[R1kaB3rN]

As of umu-launcher v1.2.6, UMU-Proton isn't a valid token so that error is expected. On the other hand, UMU-Latest is a valid token. In the README and in umu(1), by 'using UMU-Proton' we mean that when the environment variable PROTONPATH is not set then umu-launcher will use the latest UMU-Proton build that has been released. But given this issue, perhaps this can be clarified a bit.

Edit:

With some applications though, that variable is always present. Having it be empty results in an error as well which is not ideal.

It's the application's responsibility to not set it. While we could have a UMU-Proton token, the result would be the same as unsetting it. Unless there's a compelling argument to be made for having another token other than working around apps' bugs/deficiencies, which we do enough for Steam and winetricks, I believe there should be only one way to achieve the same result.