New push emails

[Owen Taylor <otaylor redhat com>]

I've installed my push email script. Everything is pretty much as I
proposed doing it in my earlier mail, with some improvement that were
suggested.

I did a lot of testing, but I'm there are some stupid mistakes, so:

 - If you make a commit to a git repository, and you get an error,
   please let me know.

 - If you see a commit email that looks weird or strange or confusing,
   please let me know.

If you wait a day or so you should be able to see a bunch of examples by
searching for 'src.gnome.org' in your svn-commits-list email folder.

Some particular points of note:

 - One thing that may look a bit weird is the numbering of mails
   with merges. You might see a sequence like:

    [pango] (8 commits) ...Merge branch sumerian-cuneiform
    [pango: 1/8] Fix crasher
    [pango: 8/8] Merge branch sumerian-cuneiform

  That means that 8 commits were pushed at once to the master branch. 
  The cover email will list all 8 like:

===
    2131312... Fix crasher
    a412a42... Start implementing Sumerian shaper (*)
    c123121... Use a less sticky clay (*)
    ...
    4121231... Merge branch sumerian-cuneiform

   (*) This commit already existed in another branch; no separate mail sent
===
 
  Then only the ones that are genuinely new are mailed out. This all makes
  sense, but maybe it would be better to just number as 1/2, 2/2.

 - Because of the behavior where it omits sending out detailed mails for changes
   already in the repository, you can't always tell exactly what files changed just 
   by reading mails, something that wa requested. Different ways we could attack this.

   - The cover email could contain a 'diffstat' for the entire series of commits.
   - We could extract a common prefix for all changed files and then put that
     in a header. 'X-Git-Changes-In: po/'. Or Something.
   - If we really just care about distinguishing po-file only changes, we could
     have X-Gnome-Po-Only: yes and make it easy for people to filter.

 - No cgit links yet. I didn't feel like figuring out how to map repo
   path to cgit path generically and didn't just want to hack it. Not
   hard though.

- Owen