Absolute paths for Minecraft 1.12.2 and earlier.

[AHilyard]

Purpose

Forge for Minecraft 1.12.2 and earlier do not fully support relative paths, causing some instances to fail. Here are some easy steps to reproduce the problem:

1. Create a Forge 1.12.2 instance.
2. Add the mod "Equipment Compare" to the instance.
3. Launch the instance.

It can be seen from the latest.log file that Forge has tried to search the same directory twice, once with the relative path and once with a non-normalized absolute path.
Other launchers appear use absolute paths to specify game directory and such, which bypasses this issue.

Approach

Add a check in launchInstance to bypass the relative path string replacement when the Minecraft version is 1.12.2 or lower.

[CLAassistant]

All committers have signed the CLA.

[Eskaan]

May this bug be solved by selecting the symlink option in the settings? (I think that is part of the reason we have it)

[MrEAlderson]

Can this be merged already?

[Eskaan]

Awaiting Feedback

[AHilyard]

May this bug be solved by selecting the symlink option in the settings? (I think that is part of the reason we have it)

I have just tested this and changing startup method to symlink mode does work. I guess this and the other identical issues point to another problem--why is symlink mode not the default if it fixes this problem, is there some downside?

[blarfoon]

The relative path is used to avoid the "command line too long" issue. Doing this in general could cause it again even with the relative paths. A possible fix would be to only use the absolute path for the game/assets paths?

[AHilyard]

The relative path is used to avoid the "command line too long" issue. Doing this in general could cause it again even with the relative paths. A possible fix would be to only use the absolute path for the game/assets paths?

I thought that issue was fixed in #1384? The path that needs to be specified as an absolute path is the path to the instance folder. I'm guessing all the other paths can be specified relatively, but I don't know for sure.