system git vs MacPorts git for fetching source

[Adam Mercer]

Hi

As the source for certain ports are obtained by Git I've been seeing a
problem regarding fetching the source related to a setting I have in
my ~/.gitconfig, specifically:

[push]
  default = upstream

I believe this option was added in Git-1.7.0, when source is fetched
for port that use git the fetch fails with the following error:

:debug:fetch Executing: /usr/bin/git clone -q
https://github.com/pieter/gitx.git
/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_devel_GitX/GitX/work/GitX-0.7.1
2>&1
:info:fetch error: Malformed value for push.default: upstream
:info:fetch error: Must be one of nothing, matching, tracking or current.

i.e. the system git is being used and as this does not recognise the
configuration option it is therefore failing.

Can't the MacPorts git be used in preference to the one supplied by Xcode?

Cheers

Adam