These error types are special because the message is embedded in ASCII art. I
think it would be a source of bugs if some error types had ": {source}" but
others don't. So I'm going to remove all ": {source}"s, and let the callers
concatenate them when needed.
Summary: In preparation for unifying all workspace dependencies across all
crates, let's go ahead and move the jj-cli crate into its own new directory.
This will also be a nicer and more uniform layout as we add new `jj-*` crates.
Signed-off-by: Austin Seipp <aseipp@pobox.com>
Change-Id: Icf94e7ae5f290dc8e181215727b38ada