Merge branch 'ew/mboxrd-format-am'

Teach format-patch and mailsplit (hence "am") how a line that
happens to begin with "From " in the e-mail message is quoted with
">", so that these lines can be restored to their original shape.

* ew/mboxrd-format-am:
am: support --patch-format=mboxrd
mailsplit: support unescaping mboxrd messages
pretty: support "mboxrd" output format

diff --cc builtin/log.c
Simple merge

diff --cc pretty.c
Simple merge

diff --cc t/t4014-format-patch.sh
Simple merge