Group commits based on `<type>`. If no `--group` option is
specified, the default is `author`. `<type>` is one of:
+
+--
- `author`, commits are grouped by author
- `committer`, commits are grouped by committer (the same as `-c`)
- `trailer:<field>`, the `<field>` is interpreted as a case-insensitive
be counted more than once (but only once per unique trailer value in
that commit).
+
-The contents of each trailer value are taken literally and completely.
-No mailmap is applied, and the `-e` option has no effect (if the trailer
-contains a username and email, they are both always shown).
+Shortlog will attempt to parse each trailer value as a `name <email>`
+identity. If successful, the mailmap is applied and the email is omitted
+unless the `--email` option is specified. If the value cannot be parsed
+as an identity, it will be taken literally and completely.
+--
++
+If `--group` is specified multiple times, commits are counted under each
+value (but again, only once per unique value in that commit). For
+example, `git shortlog --group=author --group=trailer:co-authored-by`
+counts both authors and co-authors.
-c::
--committer::