#!/bin/sh

GIT_DIR="$(git rev-parse --absolute-git-dir)"
dotest="$GIT_DIR/rebase-apply"

prec=4 &&
this=$(cat 2>/dev/null "$dotest/next") &&
msgnum=$(printf "%0${prec}d" $this) &&
test -f "$dotest/$msgnum" &&
message_id=$(sed -ne '
	/^[ 	]/{
		# Append continuation line to hold space
		H
		# Swap hold and pattern
		x
		# Remove the LF, making it a single line
		s/\n//
		# Swap hold and pattern back
		x
		# Discard the pattern and go on
		n
	}
	# Hold this new line, and look at what is in the hold space
	x
	# Is it the Message-ID line?  If so, spit it out and finish.
	/^[Mm][Ee][Ss][Ss][Aa][Gg][Ee]-[Ii][Dd]:[ 	]*/{
		s///p
		q
	}
	# Otherwise, check if this new line is empty
	x
	# Is it?  Then we are done with the header
	/^$/b end
	# Otherwise we need to hold onto this header line
	x
	# And start the next cycle
	b
: end
	# ??? do we want to check if we held onto the last message-id line
	# and process it here if we did???
	q
' "$dotest/$msgnum") &&

if	test -n "$message_id" &&
	head=$(git rev-parse --verify HEAD 2>/dev/null)
then
	echo "$head $message_id" >>"$GIT_DIR"/am.log &&
	(
		git show --format="%B" --no-patch HEAD |
			git interpret-trailers --no-divider \
				--trailer "Message-ID: $message_id" |
			git commit --amend --file -
	)
fi