#!/usr/bin/env bash
#
# Make a patch from one or several commits.
# Copyright (c) Petr Baudis, 2005
#
# Generate a patch with diff statistics and meta info about each commit.
#
# Note that if you want to use this as the output interface for your
# GIT tree containing changes against upstream GIT tree, please consider
# using the StGIT tool ("quilt for GIT"), which will enable you to
# update your patches seamlessly, rebase them against the latest upstream
# version, directly send them over mail, etc.
#
# OPTIONS
# -------
# -d DIRNAME:: Create patches in the DIRNAME directory
#	Split the patches to separate files with their names in the
#	format "%02d.patch", created in directory DIRNAME (will be
#	created if non-existent). Note that this makes sense only
#	when generating patch series, that is when you use the -r
#	argument.
#
# -f FORMAT:: Specify patch file name format
#	Format string used for generating the patch filename when
#	outputting the split-out patches (that is, passed the -d
#	option). This is by default "%s/%02d-%s.patch". The first %s
#	represents the directory name and %d represents the patch
#	sequence number. The last %s is mangled first line of the
#	commit message - kind of patch title.
#
# -m::	Base the diff at the merge base
#	Base the patches at the merge base of the -r arguments
#	(defaulting to HEAD and origin).
#
# -r FROM_ID[..TO_ID]::	Limit to revision range
#	Specify a set of commits to make patches from using either
#	'-r FROM_ID[..TO_ID]' or '-r FROM_ID -r TO_ID'. In both cases the
#	option expects IDs which resolve to commits and will include the
#	specified IDs. If 'TO_ID' is omitted patches for all commits
#	from 'FROM_ID' to the initial commit will be generated. If no
#	`-r` option is given the commit ID defaults to 'HEAD'.
#
# -s:: Omit patch header
#	Specify whether to print a short version of the patch without
#	a patch header with meta info such as author and committer.
#
# EXAMPLE USAGE
# -------------
# To make patches for all commits between two releases tagged as
# 'releasetag-0.9' and 'releasetag-0.10' do:
#
#	$ cg-mkpatch -r releasetag-0.9..releasetag-0.10
#
# The output will be a continuous dump of patches each separated by
# the line:
#
#	!-------------------------------------------------------------flip-
#
# NOTES
# -----
# The ':' is equivalent to '..' in revisions range specification (to make
# things more comfortable to SVN users). See cogito(7) for more details
# about revision specification.

USAGE="cg-mkpatch [-m] [-s] [-r FROM_ID[..TO_ID] [-d DIRNAME]]"
_git_requires_root=1

. "${COGITO_LIB}"cg-Xlib || exit 1

showpatch()
{
	header="$(mktemp -t gitpatch.XXXXXX)"
	patch="$(mktemp -t gitpatch.XXXXXX)"
	id="$1"
	cg-diff -p -r "$id" >"$patch"
	git-cat-file commit "$id" | while read -r key rest; do
		case "$key" in
		"author"|"committer")
			date=(${rest#*> })
			showdate ${date[*]}; pdate="$_showdate"
			[ "$pdate" ] && rest="${rest%> *}> $pdate"
			echo "$key" "$rest" >>"$header"
			;;
		"")
			cat
			if [ ! "$omit_header" ]; then
				echo
				echo ---

				echo commit "$id"
				cat "$header"
				echo
				cat "$patch" | git-apply --stat
			fi
			;;
		*)
			echo "$key" "$rest" >>"$header"
			;;
		esac
	done
	echo
	cat "$patch"
	rm "$header" "$patch"
}


omit_header=
log_start=
log_end=
mergebase=
outdir=
fileformat="%s/%02d-%s.patch"
while optparse; do
	if optparse -s; then
		omit_header=1
	elif optparse -r=; then
		if echo "$OPTARG" | fgrep -q '..'; then
			log_end="${OPTARG#*..}"
			[ "$log_end" ] || log_end="HEAD"
			log_start="${OPTARG%..*}"
		elif echo "$OPTARG" | grep -q ':'; then
			log_end="${OPTARG#*:}"
			[ "$log_end" ] || log_end="HEAD"
			log_start="${OPTARG%:*}"
		elif [ -z "$log_start" ]; then
			log_start="$OPTARG"
		else
			log_end="$OPTARG"
		fi
	elif optparse -m; then
		mergebase=1
	elif optparse -d=; then
		outdir="$OPTARG"
	elif optparse -f=; then
		fileformat="$OPTARG"
	else
		optfail
	fi
done

if [ "$mergebase" ]; then
	[ "$log_start" ] || log_start="HEAD"
	[ "$log_end" ] || log_end="origin"
	id1="$(cg-object-id -c "$log_start")" || exit 1
	id2="$(cg-object-id -c "$log_end")" || exit 1
	conservative_merge_base "$id1" "$id2" || exit 1
	[ "$_cg_base_conservative" ] &&
		warn -b "multiple merge bases, picking the most conservative one"
	log_start="$_cg_baselist"
fi

if [ "$log_end" ]; then
	id1="$(cg-object-id -c "$log_start")" || exit 1
	id2="$(cg-object-id -c "$log_end")" || exit 1

	if [ "$outdir" ]; then
		mkdir -p "$outdir" || die "cannot create patch directory"
		pnum=001
	fi

	git-rev-list --topo-order "$id2" "^$id1" | tac | while read id; do
		if [ "$outdir" ]; then
			title="$(git-cat-file commit "$id" |
			         sed -n '/^$/{n;
				              s/^[ \t]*\[[^]]*\][ \t]*//;
				              s/[:., \t][:., \t]*/-/g;
					      s/_/-/g;
					      # *cough*
					      y/ABCDEFGHIJKLMNOPQRSTUVWXYZ/abcdefghijklmnopqrstuvwxyz/;
					      s/[^a-zA-Z0-9-]//g;
				              p;q;}')"
			filename="$(printf "$fileformat" "$outdir" "$pnum" "$title")"
			echo "$filename"
			showpatch "$id" >"$filename"
			pnum=$((pnum+1))
		else
			showpatch "$id"
			echo
			echo
			echo -e '\014'
			echo '!-------------------------------------------------------------flip-'
			echo
			echo
		fi
	done

else
	[ "$outdir" ] && die "-d makes sense only for patch series"
	id="$(cg-object-id -c "$log_start")" || exit 1
	showpatch "$id"
fi