Add summary fields

[guenhter]

Add a few more fields to the summary:

$ git summary                                                                                                                                                                                   

 project     : configservice
 repo age    : 3 months
 last active : 3 weeks ago  (new)
 active on   : 9 days   (renamed from "active" -> "active on")
 commits     : 20
 files       : 45
 uncommitted : 1      (new)
 authors     :
     8  Michael Mayr   40.0%
     5  Simon Gaudek   25.0%
     5  guenthgr       25.0%
     2  Günther Grill  10.0%

[spacewander]

Let's update the doc relative to this command

[spacewander]

Suggested change

	git log --pretty=oneline --format="%ar" | head -n 1
	git log --pretty=oneline --format="%ar" -n 1

[guenhter]

Done

[spacewander]

Let's update the md file and generate the doc via https://github.com/tj/git-extras/tree/master/man#how-to-generate-documentation

[spacewander]

And also this: https://github.com/tj/git-extras/blob/master/Commands.md#git-summary

[guenhter]

:) oh I see. Only the MD file must be manually adapted. When modifiying the x.1 file I already wondered how people can modify this file with all the tags and making no mistake. Thx for pointing this out.

[spacewander]

Don't forget the https://github.com/tj/git-extras/blob/master/Commands.md#git-summary

[guenhter]

@spacewander Done.