When we resolve aliases and we try to resolve something that is not a
real command and not an alias, we currently replicate `clap`'s error
message. I don't know why I did that because it seems that we should
just stop resolving aliases and let `clap` try to parse what we have
resolved at that point. This patch makes that change, thereby removing
an additional call to `process::exit()`.
In many of these places, we don't need an owned value, so using a
reference means we don't force the caller to clone the value. I really
doubt it will have any noticeable impact on performance (I think these
are all once-per-repo paths); it's just a little simpler this way.
This commit moves much of the `commands` module that isn't specific to
a particular command into a new `cli_util`.
Much of this is actually not even CLI-specific, so we should move that
further down into the library, but that can come later. That includes
the code in `WorkspaceCommandHelper` for snapshotting the working copy
and automatically importing/exporting to a colocated Git working copy.
