Merge branch 'jk/chopped-ident'

A commit object whose author or committer ident are malformed
crashed some code that trusted that a name, an email and an
timestamp can always be found in it.

* jk/chopped-ident:
blame: handle broken commit headers gracefully
pretty: handle broken commit headers gracefully
cat-file: print tags raw for "cat-file -p"

diff --cc pretty.c
Simple merge