As a developer, I want to be able to use feature branches

[z]

NetRadiant generates a name sequentially in form for "brush1" when adding a brush to a .map file. Because of this, feature branches, or even working in parallel is difficult.

Mapper A and B branch off master with current brush index brush50, both mappers add 4 brushes. Both maps now end in brush54, but brush 51, 52, 53, 54 represent two different things in each branch.

The proposed, admittedly hacky workflow is to re-namespace or re-index the feature branches as they before merge.

[MarioSMB]

Ideally, we should just turn off numbering (I believe this is an option in NetRadiant - not sure how the main repos enforce it).