We had both `repo()` and `mut_repo()` on `Transaction` and I think it
was easy to get confused and think that the former returned a
`&ReadonlyRepo` but both of them actually return a reference to
`MutableRepo` (the latter obviously returns a mutable reference). I
hope that renaming to the more idiomatic `repo_mut()` will help
clarify.
We could instead have renamed them to `mut_repo()` and
`mut_repo_mut()` but that seemed unnecessarily long. It would better
match the `mut_repo` variables we typically use, though.
Now, the command for `jj git remote add` is `cmd_git_remote_add` and its
argument type is `GitRemoteAddArgs`. This should make it easier to find
the CLI docs and the implementation for commands.
This is how `jj branch` commands were already set up in this way. The
`jj op` commands were also already set up in this way, except the
functions are called e.g. `cmd_op_undo`, I kept this for simplicity.
I was mainly motivated by the `jj file` commands. Most other commands
had functions already named in the above pattern, but used to have
shorter argument type names.
