fix: Fix 'find' command short format.

[alilleybrinker]

Previously, the 'short' format on the 'find' command would actually
just re-print the hash that was provided, as it was treating the
output identically to the id command. This commit introduces a new
Msg constructor for the find version, which is identical to the
id version for the plain and json formats, but which only
prints the found path in the 'short' format.

It also slightly refactors printing in Msg to avoid the trait object
and instead just match on the message status to decide where to write.

Signed-off-by: GitHub [email protected]