Set git diff to a default value

I previously changed my git diff tool with git config --global diff.external <diff-tool-name>. I decided I don't like开发者_开发知识库 that tool and wanted to switch back.

I tried meddling around and did something like: git config --global diff.external git-diff. Now calling git diff to see unstaged changes yields:

fatal: ambiguous argument '48e66b706d21398f28240810e7fc0d44d8f92d99': unknown revision or path not in the working tr
Use '--' to separate paths from revisions
external diff died, stopping at somefile.ext.

How do I set my git diff command to use the default command line git diff that came with git. Something like:

git config --global diff.

and then what?

---

Try
git config --global --unset diff

and

git config --global --unset diff.external

See the explanation of git config for further details.