Thankfully, Git is highly configurable, and the fix is rather easy:
- Set i18n.commitencoding to the codepage you're on in cmd.exe (I'm on windows-1252)
- Set i18n.logoutputencoding to the same codepage.
- Set the LESSCHARSET environment variable to a proper name for the code page you're on (I'm on latin1), either by adding a user environment variable in Control Panel > System and Security > System > Advanced System Settings > Advanced > Environment Variables..., or setting it your cmd.exe session (e.g. set LESSCHARSET=latin1).
git config --global i18n.commitencodig windows-1252
git config --global i18n.logoutputencoding windows-1252
The first setting tells Git how your commit messages, including your author information, are encoded. The second tells Git what encoding it should use when writing output from a command like git log. The third and final setting tells less, the pager that Git runs git log output through, what encoding to use.