Sometimes it's necessary to -- for one's sanity, if nothing else -- to
establish a set of generally non-controversial, sane, system-wide git
configuration defaults. This is largely helpful when multiple people are
using the same system who may not have a standard
carry around with them.
To do this, we can leverage the little-used system-wide git config file at
/etc/gitconfig. Remember that by default git looks at three files to
determine its configuration (in ascending order of priority):
~/.gitconfig(user aka global), and
.git/config(configuration for the current repository).
This allows us to set defaults in the system configuration file without
interfering with people who prefer different settings: their global config at
~/.gitconfig will win.
This config sets a couple safer defaults for pushing, makes git merge/diff/rebase a little more DWIM, causes the committer, as well as the author, information to be displayed by default, as well as allowing for an easy way to override the system config on a per-system basis. (In case, say, you're using puppet or the like to distribute this configuration across multiple hosts.)
And... As with all things "generally non-controversial", remember that these are the sorts of things likely to touch off religious wars. The goal here is for a sane set of defaults for all users, not The One True Way To Do GIT. That's what user global configs are for :)