>> Yes, some adjustment is needed for grep.  That reminded me
>> about two unclosed feature requests: bug#13417 and bug#14017
>> that proposed to display these numbers also at the bottom of
>> output buffers.  But the showstopper was to decide on the
>> final format of such messages.  Although this looks good:
>> 
>>   Grep finished with 42 matches in 5 lines at Thu Jul 21 15:02:15
>> 
>> Than the mode-line will display two numbers: the number of matches
>> and the number of matching lines (in green).
>
> Is the total number of lines (in the search space) also
> available?  If so, would that be useful?  Maybe something
> like this?
>
> Grep finished at Thu Jul 21 15:02:15 - 42 matches in 5/113 lines 
>                                                       ^^^^

Unfortunately the total number of lines is not available.
There is even problems with getting the right number of matches.
When grep doesn't highlight matches, we can't count them.

Another problem is that grep matches to be printed at the end of the
grep buffer can't be counted in grep-regexp-alist because it is
based on font-lock which is invoked at unpredictable times
when grep process is already finished.  This leaves only one way
to count matches in grep-filter in this patch.

For the same reason, printing the number of compilation errors at
the end of the compilation buffer can't be implemented for bug#13417.