.gitignore ignores files locally, but it is intended to be committed to the repository and shared with other contributors and users. You can set a global .gitignore, but then all your repositories would share those settings.

If you want to ignore certain files in a repository locally and not make the file part of any repository, edit .git/info/exclude inside your repository.

For example:

# these files are only ignored on this repo
# these rules are not shared with anyone
# as they are personal                                              
gtk_tests.py
gui/gtk/tests/*
localhost
pushReports.py
server/