new_commit ::= 'commit' sp ref_str lf
mark?
- ('author' sp name sp '<' email '>' sp when lf)?
- 'committer' sp name sp '<' email '>' sp when lf
+ ('author' (sp name)? sp '<' email '>' sp when lf)?
+ 'committer' (sp name)? sp '<' email '>' sp when lf
commit_msg
('from' sp committish lf)?
('merge' sp committish lf)*
new_tag ::= 'tag' sp tag_str lf
'from' sp committish lf
- ('tagger' sp name sp '<' email '>' sp when lf)?
+ ('tagger' (sp name)? sp '<' email '>' sp when lf)?
tag_msg;
tag_msg ::= data;