#!/bin/bash
#
# A hook script to check the commit log message to ensure that it has
# a well-formed commit summary and body, a valid Signed-off-by: line,
# and a Gerrit Change-Id: line (added automatically if missing).
#
# Called by git-commit with one argument, the name of the file
# that has the commit message.  The hook should exit with non-zero
# status after issuing an appropriate message if it wants to stop the
# commit.  The hook is allowed to edit the commit message file.
#
# Should be installed as .git/hooks/commit-msg.
#

ORIGINAL="$1"
REVISED="$(mktemp "$1.XXXXXX")"
SIGNOFF="Signed-off-by:"
CHANGEID="Change-Id:"
WIDTH_SUM=64
WIDTH_REG=70

# Check for, and add if missing, a unique Change-Id
new_changeid() {
	{
		git var GIT_AUTHOR_IDENT
		git var GIT_COMMITTER_IDENT
		git write-tree
		git rev-parse HEAD 2>/dev/null
		grep -v "$SIGNOFF" "$ORIGINAL" | git stripspace -s
	} | git hash-object --stdin
}

usage() {
	[ "$LINE" ] && echo "error:$NUM: $LINE" 1>&2 && echo "" 1>&2

	cat 1>&2 <<- EOF
	Commit message $1
	$2
	See http://wiki.whamcloud.com/display/PUB/Submitting+Changes
	for full details.  An example valid commit comment is:

	LU-nnn component: short description of change under 64 columns

	A more detailed explanation.  This can be as detailed as you'd like.
	Please explain both what problem was solved and a good high-level
	description of how it was solved.  Wrap at $WIDTH_REG columns or less.

	$SIGNOFF Your Real Name <your_email@domain.name>
	$CHANGEID Ixxxx(added automatically if missing)xxxx
	EOF

	exit 1
}

export HAS_SIGNOFF=false
export HAS_SUMMARY=false
export HAS_BLANK=false
export HAS_COMMENTS=false
export HAS_DIFF=false

grep -q "^$CHANGEID" "$ORIGINAL" && HAS_CHANGEID=true || HAS_CHANGEID=false

export LINE=""
export NUM=1

IFS=""
while read LINE; do
	WIDTH=$(($(echo $LINE | wc -c) - 1)) # -1 for end-of-line character

	case "$LINE" in
	$SIGNOFF*)
		$HAS_SUMMARY || usage "missing summary before $SIGNOFF."
		$HAS_BLANK || usage "missing blank line before $SIGNOFF."
		# Signed-off-by: First Last <email@host.domain>
		GOOD=$(echo "$LINE" | grep "^$SIGNOFF .* .* <.*@[^.]*\..*>")
		[ -z "$GOOD" ] &&
			usage "missing valid commit summary line to show" \
			      "agreement with code submission requirements at"
		HAS_SIGNOFF=true
		echo $LINE
		$HAS_CHANGEID || echo "$CHANGEID I$(new_changeid)"
		;;
	$CHANGEID*)
		$HAS_SUMMARY || usage "missing summary before $CHANGEID line."
		$HAS_BLANK || usage "missing blank line before $CHANGEID line."
		# Change-Id: I762ab50568f25527176ae54e92c446cf06112097
		GOOD=$(echo "$LINE" | grep "^$CHANGEID I[0-9a-fA-F]\{40\}")
		[ -z "$GOOD" ] &&
			usage "missing valid $CHANGEID line for Gerrit tracking"
		HAS_CHANGEID=true
		echo $LINE
		;;
	"")	[ $HAS_SUMMARY -a $NUM -eq 2 ] && HAS_BLANK=true
		echo $LINE
		;;
	diff*|index*) # beginning of uncommented diffstat from "commit -v"
		# diff --git a/build/commit-msg b/build/commit-msg
		# index 80a3442..acb4c50 100755
		DIFF=$(echo "$LINE" | grep -- "^diff --git a/")
		[ "$DIFF" ] && HAS_DIFF=true && continue
		INDEX=$(echo "$LINE" | grep -- "^index [0-9a-fA-F]\{6,\}\.\.")
		[ $HAS_DIFF -a "$INDEX" ] && break || HAS_DIFF=false
		;;
	\#*)	HAS_COMMENTS=true
		continue
		;;
	*)	if [ $NUM -eq 1 ]; then
			FMT="^[A-Z]\{2,5\}-[0-9]\{1,5\} [-a-z0-9]\{2,9\}: "
			GOOD=$(echo "$LINE" | grep "$FMT")
			[ $WIDTH -gt $WIDTH_SUM ] &&
				usage "summary longer than $WIDTH_SUM columns."
			if [ -z "$GOOD" ]; then
				FMT="^[A-Z]\{2,5\}-[0-9]\{1,5\} "
				NO_SUBSYS=$(echo "$LINE" | grep "$FMT")
				[ "$NO_SUBSYS" ] &&
					usage "has no subsys: in commit summary"
				usage "missing valid commit summary line."
			fi
			HAS_SUMMARY=true
		elif [ $WIDTH -gt $WIDTH_REG ]; then
			usage "has lines longer than $WIDTH_REG columns."
		fi
		HAS_DIFF=false
		echo $LINE
		;;
	esac

	NUM=$((NUM + 1))
done < "$ORIGINAL" > "$REVISED"

[ $NUM -eq 1 ] && exit 1 # empty file

LINE=""
$HAS_SUMMARY || usage "missing commit summary line."
$HAS_SIGNOFF || usage "missing $SIGNOFF line."
$HAS_CHANGEID && rm "$REVISED" || mv "$REVISED" "$ORIGINAL"