Correctly ignore all files recursively under a specific folder except for a specific file type

@SimonBuchan is correct.

Since git 1.8.2, Resources/** !Resources/**/*.foo works.

The best answer is to add a Resources/.gitignore file under Resources containing:

# Ignore any file in this directory except for this file and *.foo files
*
!/.gitignore
!*.foo

If you are unwilling or unable to add that .gitignore file, there is an inelegant solution:

# Ignore any file but *.foo under Resources. Update this if we add deeper directories
Resources/*
!Resources/*/
!Resources/*.foo
Resources/*/*
!Resources/*/*/
!Resources/*/*.foo
Resources/*/*/*
!Resources/*/*/*/
!Resources/*/*/*.foo
Resources/*/*/*/*
!Resources/*/*/*/*/
!Resources/*/*/*/*.foo

You will need to edit that pattern if you add directories deeper than specified.

This might look stupid, but check if you haven't already added the folder/files you are trying to ignore to the index before. If you did, it does not matter what you put in your .gitignore file, the folders/files will still be staged.