Do not track "*.aux.xml" files.

[Benjamin Jakimow]

Often *.aux.xml files are changed on each gdal / QGIS file access. This forces unncessesary git commits. Avoid by:

1. add *.aux.xml to .gitignore
2. untrack *.aux.xml files on all machines.

# Do this on all machines
echo "FILE_NAME" >> .gitignore
git rm --cached FILE_NAME
git add -u
git commit -m "removing files from version control"
# Sync with your git server, pull to sync and push to register your local change
git pull
git push

Found in http://arlocarreon.com/blog/git/untrack-files-in-git-repos-without-deleting-them/