Ability to set alternate base directory?

Nobody has claimed this yet.

I've been working on a game that has a strict hierarchy for resource organization, and one problem that's come up is that in order for the maps created in Tiled to have the proper file paths for tilesets and such, we must edit the map in the same directory as the game's executable, then copy the map into its proper location in the hierarchy. We could modify our game engine to prepend the directory that the map is in to any file paths in a map automatically, but it would be far more convenient, and would make more sense (imo) to instead have a feature in Tiled that lets us set a different base path in Tiled so the file paths in maps automatically account for our hierarchy.

I wrote this late at night, so if I'm not making sense, I apologize.

No files, tests, or entry points are named. Start by locating how Tiled resolves map-relative tileset and resource paths, then determine where an alternate base directory could be configured. Done means maps can be edited outside the executable directory while preserving the intended paths in the game's hierarchy.

Written by the indexing model from the issue text.