Most package maintainers already know this (or use something way easier), but this is how I go about updating all my fedora package git folders:

[ankur@ankur ~]$ cd Documents/work/repos/others/fedora-packages/
[ankur@ankur fedora-packages]$ ls
aeskulap  dcm4che-test       fpaste        hiran-perizia-fonts  libmpd       memaker                OpenNL                python-hl7  subversion    trash-cli
cmake     detex              freemedforms  Inventor             libtorrent   mpdas                  OSGi-bundle-ant-task  rssdler     suitesparse   vtk
comps     django-authopenid  gdcm          klt                  libtpcimgio  nifticlib              pyclutter             rtorrent    toothchart    xmedcon
curlpp    evolution-rss      gnumed        libgexiv2            libtpcmisc   oldstandard-sfd-fonts  pystache              scout       transmission  zlib
[ankur@ankur fedora-packages]$ for i in `ls`; do cd "$i"; git pull; cd ..; done
remote: Counting objects: 5, done.
remote: Compressing objects: 100% (3/3), done.
Unpacking objects: 100% (3/3), done.
remote: Total 3 (delta 2), reused 0 (delta 0)
From ssh://pkgs.fedoraproject.org/aeskulap
 * [new branch]      f17        -> origin/f17
   ca0fa88..ef4f943  master     -> origin/master
Updating ca0fa88..ef4f943
Fast-forward
 aeskulap.spec |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
remote: Counting objects: 20, done.
remote: Compressing objects: 100% (17/17), done.
..

Moments later, all of them are up to date.