Colocation is about sharing the working copy between jj and git. It's
less important where the repo is stored. I therefore think we should
not call it "colocated repo". I considered renaming it to "colocated
working copy" but that sounded awkward in many places because we often
talk about the whole workspace (repo + working copy), so "In colocated
workspaces with a very large number of branches or other refs" sounds
better than "In colocated working copies with a very large number of
branches or other refs".
Once we support colocate workspaces in non-main Git worktrees, I think
this rename will be even more relevant because then all those
workspaces share the same repo but only some of them may be colocated.
This new command lets you turn a non colocated git repo into a colocated repo or vice-versa (by using the `jj git colocation enable` and `jj git colocation disable` commands respectively).
These commands simply implement the instructions found in https://github.com/jj-vcs/jj/blob/main/docs/git-compatibility.md#converting-a-repo-into-a-co-located-repo
You can also call `jj git colocation status` to show the current colocation status and `jj colocation` to show a help message (with the list of sub-commands).
