Telling git its ok to remove untracked files

You need git clean but add the -df to enable removing files that are in directories from where you are. Add x to include ignored files.

So to completely clean your working directory leaving only what is in source control, issue this command:

git clean -xdf

You may be looking for git clean. This will delete all untracked files. By default this ignores (does not delete) patterns in .gitignore, but git clean -x cleans those files too.

From the git clean man page:

   -x
       Don't use the ignore rules. This allows removing all untracked
       files, including build products. This can be used (possibly in
       conjunction with git reset) to create a pristine working directory
       to test a clean build.