When trying to update your local copy from remote master copy, you will see following error
$ git pull origin master
error: Your local changes to the following files would be overwritten by merge:
<list of files>
Please commit your changes or stash them before you merge.
Aborting
You have several options here
Commit the change
$ git add .
$ git commit -m "committing before the update"
Stash them
$ git stash
$ git stash pop
Overwrite local changes
git reset --hard