[GSoC] Some #leftoverbits for anyone looking for little projects

In lieu of sending a PR to https://git.github.io/SoC-2018-Microprojects/ I thought I'd list a few more suggestions, and hopefully others will chime in.

This is all TODO stuff I've been meaning to do myself, but wouldn't mind at all if someone else tackled.

I'm not interested in mentoring GSoC, but these are all small enough to need to special help from me (or anyone in particular), and if nobody picks them up I can refer back to this mail for my own use.

 * Having grep support the -o option like GNU grep et al.

   We have most of the code for this already in the form of our color
   hi-lighting, it would mostly just be a matter of "just print out the
   stuff you'd have colored", with the small exception that if you have
   more than one match on a line they should be printed out on their own
   lines.

 * Give "rebase -i" some option so when you "reword" the patch is
   included in the message.

   I keep going to the shell because I have no idea what change I'm
   describing.

 * Add more config IncludeIf conditions.

   Recently there was a mention on git-users to excend the includeIf
   statement to read config:
   https://groups.google.com/forum/?fromgroups#!searchin/git-users/includeif%7Csort:date/git-users/SHd506snwSk/UdVCsCILBwAJ

   Now that seems like a nasty circular dependency but there's other
   low-hanging fruit there, like make it match a given env name to a
   value (or glob?).

 * Add another set of GIT_{AUTHOR,COMMITTER}_{NAME,EMAIL} with lower
   priorities.

   There is a script at work which I have to manually blacklist which
   sets git author names & e-mails via LDAP for all logged in users via
   /etc/profile (and gets my name wrong)[1].

   It would be nice if git supported a way to do this that didn't either
   involve overriding everything (as the current env vars do) or munging
   the user's ~ config (ew!). I.e. the priority of these new env vars
   would come after reading from the config, not overriding the config
   as the current ones do. So it could be used to make a suggestion if
   no other value was found.

 * Write git-unpack-{refs,objects}

   I don't know if this is small enough (maybe the refs part?). This
   would give you purely loose objects & refs. This is a terrible idea
   for any "real" use, but very useful for testing.

   Now when I'm testing repack I need to keep an old copy of the repo
   around, because there's no easy way (that I know of) to pack things
   and then get back to loose object state. Ditto for packing refs.

 * I had a previous TODO list of "small" things at
   https://public-inbox.org/git/CACBZZX5wdnA-96e11edE7xRnAHo19RFTrZmqFQj-0ogLOJTncQ@mail.gmail.com/

1. At work like in so many companies LDAP is synced everywhere, but of
   course that means catering to the lowest common denominator. Last I
   heard attempts to give me a non-ASCII name (in the GEOS field) had
   failed because some phone or printer somewhere refused to accept it.