If you mean you want the pull to overwrite local changes, doing the merge as if the working tree were clean, well, clean the working tree:
git reset --hard
If there are untracked local files you could use
git clean to remove them. Use
git clean -f to remove untracked files,
-df to remove untracked files and directories, and
-xdf to remove untracked or ignored files or directories.
If on the other hand you want to keep the local modifications somehow, you'd use stash to hide them away before pulling, then reapply them afterwards:
git stash pop
I don't think it makes any sense to literally ignore the changes, though - half of pull is merge, and it needs to merge the committed versions of content with the versions it fetched.