How to git ignore subfolders / subdirectories?

You can use .gitignore in the top level to ignore all directories in the project with the same name. For example:

Debug/
Release/

This should update immediately so it's visible when you do git status. Ensure that these directories are not already added to git, as that will override the ignores.

All the above answers are valid, but something that I don't think is mentioned is that once you add a file from that directory into the repo, you can't ignore that directory/subdirectory that contains that file (git will ignore that directive).

To ignore already added files run

$ git rm -r --cached .

Otherwise you'll have to remove all files from the repo's target directory first - and then you can ignore that folder.

The question isn't asking about ignoring all subdirectories, but I couldn't find the answer anywhere, so I'll post it: */*.

Have you tried wildcards?

Solution/*/bin/Debug
Solution/*/bin/Release

With version 1.8.2 of git, you can also use the ** wildcard to match any level of subdirectories:

**/bin/Debug/
**/bin/Release/