>> -		  (message "Running %s in background..." full-command))
>> +		  (message "Running  in background: %s" full-command))
>                                    ^^
> Extra blank.
>
>> -		   (message "Running %s in background... done" full-command))))
>> +		    (let ((message-truncate-lines t))
>> +		      (message "Finished in background: %s" full-command)))))
>
> I find the original more in line with what we do elsewhere in Emacs.
> If the problem is that "done" could be truncated, then please use
>
>   Done in background: %s

Then extra blank is not needed when using “Done in background” because it
would require too many blanks to align with “Finished in background”.

>> -	      (error "Running %s...FAILED (%s)" full-command
>> -		     (if (integerp status) (format "status %d" status) status)))
>> +	      (error "Failed (%s): %s"
>> +                     (if (integerp status) (format "status %d" status) status)
>> +		     full-command))
>>  	    (when vc-command-messages
>> -	      (message "Running %s...OK = %d" full-command status))))
>> +	      (message "Success (%d): %s" status full-command))))
>
> "Failed" and "Success" don't go together well, as they use different
> grammatical form.  How about using "Done" here as well?  And won't
> status always be zero when it succeeds?  If not, I'd use

I see that the status in case of success is 1.

>   Done (status=%d): %s

Done in the following patch: