"U" for a good signature with unknown validity and "N" for no signature
- '%GS': show the name of the signer for a signed commit
- '%GK': show the key used to sign a signed commit
-- '%gD': reflog selector, e.g., `refs/stash@{1}`
-- '%gd': shortened reflog selector, e.g., `stash@{1}`
+- '%gD': reflog selector, e.g., `refs/stash@{1}` or
+ `refs/stash@{2 minutes ago`}; the format follows the rules described
+ for the `-g` option
+- '%gd': shortened reflog selector, e.g., `stash@{1}` or
+ `stash@{2 minutes ago}`
- '%gn': reflog identity name
- '%gN': reflog identity name (respecting .mailmap, see
linkgit:git-shortlog[1] or linkgit:git-blame[1])