"git format-patch --from=<ident>" can be told to add an in-body
"From:" line even for commits that are authored by the given
<ident> with "--force-in-body-from"option.
* jc/format-patch-force-in-body-from:
format-patch: learn format.forceInBodyFrom configuration variable
format-patch: allow forcing the use of in-body From: header
pretty: separate out the logic to decide the use of in-body from