display output in some succinct mode

[nosarthur]

gita fetch and gita pull could create a lot of screen output, which is not particularly useful (I never looked at them myself). It would be nice to have a succinct output.

@seqizz suggested to use progress bars for the updated repos, like docker pull output. For example,

reponame  branch  ###==== Updating...
reponame2  branch  ######## Failed (There is no tracking information for the current branch.)
reponame3  branch  ######## Done (2 new branches fetched, 1 file changed, 46 insertions(+))
reponame3  branch  ######## Done (Already up-to-date)
reponame4  branch  ######## Done (2 file changed, 12 insertions(+), 4 deletions(-))

I think this is very neat. However, it's not clear to me how to compute the progress. Please leave a comment if you have any ideas.

As for the bookkeeping of which subcommands are in succinct mode, we can introduce another tag in the yaml configuration file, say succinct_output or something that gives a good description of the final implementation. Then users can personalize their preferences, e.g., overriding default behavior, controlling their custom command (is it possible to have a universal solution to compute progress/summaries?).

[dgrant]

Strongly agree... I just ran gita super status and I get a bunch of output but I have no way of knowing which output is for which repo.

[dgrant]

See PR #66