#!/bin/bash

commit=$1
[ "$commit" ] || {
	echo "$0: <commit id> [<top tag> [<linus branch>]]" 1>&2
	exit 1
}
commit=$(git rev-parse --verify "$commit")
[ "$commit" ] || {
	echo "No such commit" 1>&2
	exit 1
}

top=$2
[ "$top" ] || top=HEAD
tcommit=$(git rev-parse --verify "$top")
[ "$tcommit" ] || {
	echo "Bad top tag" 1>&2
	exit 1
}

linus=$3
[ "$linus" ] || linus=origin/master
lcommit=$(git rev-parse --verify "$linus")
[ "$lcommit" ] || {
	echo "Bad linus branch" 1>&2
	exit 1
}

base=$(git merge-base "$linus" "$top")

git log --first-parent --reverse --pretty='format:%H %P' "$base".."$top" |
while read m p1 p2
do
	[ "$p1" = "$commit" ] && {
		git show -s --pretty="format:Commit:		%H%nAuthor:		%aN <%aE>%nAuthorDate:	%ad%nCommitter:	%cN <%cE>%nCommitterDate:	%cd%nSubject:	%s" $p1
		break
	}
	[ "$p2" ] ||
		continue
	git rev-list $base..$p2 | grep -q "$commit" || continue
	git show -s --pretty="format:Commit:		%H%nAuthor:		%aN <%aE>%nAuthorDate:	%ad%nCommitter:	%cN <%cE>%nCommitterDate:	%cd%nSubject:	%s" $m
	break
done

exit 0