undoing commited changes in git for a file code example

Example 1: git discard local changes

# Discarding local changes (permanently) to a file:
git checkout -- <file>

# Discard all local changes to all files permanently:
git reset --hard

Example 2: git abort changes

git stash save --keep-index --include-untracked
You don't need to include --include-untracked if you don't want to be thorough about it.

After that, you can drop that stash with a git stash drop command if you like.