Quieting ``mr`` output

[Michael Henry]

On 06/25/2015 01:49 PM, John Whitley wrote:
> Nice idea, Michael.  It’s possible to prepend text only if
> some command has output.

I've never seen that particular trick with ``sed``, but I like
it.  It's very compact and uses a standard tool instead of
hundreds of lines of Python, which makes it a much better
candidate for inclusion in ``mr`` or ``vcsh`` directly.  The
only thing it lacks is a display of "progress" as the
repositories are being checked.  For ``mr status`` using git
repositories on my desktop with RAID SSDs, the difference isn't
significant, as the entire operation completes in under half a
second; but for commands like ``mr update``, I find it nice to
see the activity as it progresses (especially on a slower link).
In addition, some commands generate output even in the
"uninteresting" cases.  For example, a default ``mr update``
looks like this::

  mr update: /home/mike/.
  Already up-to-date.

  mr update: /home/mike/projects/ProjectOne
  Already up-to-date.

  [...]

  mr update: /home/mike/projects/ProjectN
  Already up-to-date.

I'd like to be able to squelch this kind of output as well.  But
if you're willing to forgo seeing the progress "live" as it
happens, then such lines could be removed by additional ``sed``
logic.

For most users, having something like your ``sed``-based
implementation built-in would be advantageous, though for myself
I'd find it nice (but not absolutely necessary) if that feature
could be bypassed to allow a display of "progress" as the
overall operation proceeds.

Thanks,
Michael Henry