Remove unwanted files from a git repo AFTER adding a .gitignore.

# See the unwanted files:
git ls-files -ci --exclude-standard

# Remove the unwanted files: 
git ls-files -ci --exclude-standard -z | xargs -0 git rm --cached

# Commit changes
git commit -am "Removed unwanted files marked in .gitignore"

# Push
git push origin master # or whatever branch you're on

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