pacman-pacnew

#!/bin/bash

usage() {
	bin=$(basename $0)
	echo >&2 "Usage:"
	echo >&2 "  $bin [ opts ] { -a | --auto }"
	echo >&2 "  $bin [ opts ] [ -s | --no-updatedb ] { -l | --locate }"
	echo >&2 "  $bin [ opts ] file [ file ... ]"
	echo >&2 "Where [ opts ] can be: [-x] [ -y | --yes ] [ -o | --old | -n | --new ]"
	echo >&2
	echo >&2 "Tool to merge Arch Linux' pacman .pacnew config file replacements with existing ones."
	echo >&2
	echo >&2 "Without -o/--old or -n/--new options will use 'git add -p' for interactive merging."
	echo >&2 "List of files can either be specified explicitly,"
	echo >&2 " grepped from pacman.log (-a/--auto option), or found by locate (-l/--locate option)."
	echo >&2 "Order of options is important."
	echo >&2
	echo >&2 "Regardless of --old/--new options, displays produced diff and prompts for applying it."
	echo >&2 "-y/--yes option can be used to skip 'apply diff?'"
	echo >&2 " prompt, but not the 'git add -p' part (use -o/-n opts for that)."
	exit ${1:-0}
}
[[ -z "$1" || "$1" = -h || "$1" = --help ]] && usage
[[ "$1" = -x ]] && { set -x; shift; }


set -e -o pipefail
export LC_ALL=C

ask=
[[ "$1" = -y || "$1" = --yes ]] || ask=t

use_old= use_new= updatedb=
case "$1" in
	-o|--old) use_old=t; shift;;
	-n|--new) use_new=t; shift;;
esac
[[ "$1" = -s || "$1" = --no-updatedb ]] || updatedb=t

mode= files=()
case "$1" in

	-l|--locate) mode=locate
		[[ -z "$updatedb" ]] || updatedb
		files=( $(locate -e --regex '\.pacnew$' | sed 's:\.pacnew$::' | sort -u) ) ;;

	-a|--auto) mode=auto
		n=$( awk '
			/^\[.+?\] \[PACMAN\] starting full system upgrade$/ {n=NR}
			END {print n ? n : 1}' /var/log/pacman.log )
		files=( $(sed -nr "$n"',$ s/^\[.+?\] \[ALPM\] warning:'`
			`' (.+) installed as \1.pacnew$/\1/ p' /var/log/pacman.log | sort -u) ) ;;

	*) mode=list
		[[ "${1:0:1}" != - ]] || usage 1
		files=()
		for p in "$@"; do files+=( "${p%.pacnew}" ); done ;;

esac


tmp=$(mktemp -d /tmp/.pacman-merge-confs.XXXXX)
trap "rm -rf --one-file-system '$tmp'" EXIT
cd "$tmp"


git init -q
export GIT_DIR=.git

first_file_warn=t
declare -A pbs

for p in "${files[@]}"; do
	pb=${p#/}
	pb=${pb//\//-} # should not conflict, but if it does, can be resolved manually
	[[ -z "${pbs[$pb]}" ]] || { echo >&2 "Conflicting path-filename: $pb"; exit 1; }
	[[ -e "$p".pacnew ]] || {
		if [[ "$mode" == auto ]]
		then
			[[ -z "$first_file_warn" ]] || { echo >&2; echo >&2 '  ----------'; first_file_warn=; }
			echo >&2 "WARNING: pacnew file is missing, assuming already merged: ${p}.pacnew"
			continue
		else:
			echo >&2 "ERROR: pacnew file is missing, aborting: ${p}.pacnew"
			exit 1
		fi
	}
	cp "$p".pacnew ./"$pb"
	pbs+=( [$pb]="$p" )
done
[[ -n "$first_file_warn" ]] || { echo >&2 '  ----------'; echo >&2; }

[[ ${#pbs[@]} -gt 0 ]] || {
	echo >&2 "ERROR: no files to merge specified or detected, exiting"
	exit 1
}

git add -- "${!pbs[@]}"
git commit -q -a -m 'pacnew files'
git tag pacnew

for pb in "${!pbs[@]}"; do p=${pbs[$pb]}; cp "$p" ./"$pb"; done
[[ -z "$(git clean -nd)" ]] || {
	echo >&2 "ERROR: Failed to produce clean git repo, git-clean output:"
	git clean -nd >&2
	exit 1
}


[[ -n "$use_old" || -n "$use_new" ]] || {
	echo "Running 'git add -p' for rebasing original version on top of pacnew files."
	echo "Useful commands:"
	echo "  y - apply/keep original hunk, n - use pacnew version here, s - split hunk"
	echo "  d - use pacnew for the rest of the file, a - use original for the rest of the file"
	echo

	git add -p # main interactive operation
}


[[ -n "$use_old" ]] && commit_opts=-a || commit_opts=
git commit -q --allow-empty $commit_opts -m 'migrated changes'
git tag merged

git commit -q --allow-empty -a -m 'updates and leftovers'
git tag original

[[ -z "$ask" ]] || {
	echo "Generating git-diff between original and final (merged) version:"
	echo

	git diff original merged

	echo
	read -e -p "Apply produced diff to all files [y/N]? " y
	echo

	[[ "$y" = y || "$y" == yes ]] || {
		echo >&2 "ERROR: Aborting as per user request (need: 'y' or 'yes', read: '$y')"
		exit 1
	}
}


git reset -q --hard merged

for pb in "${!pbs[@]}"; do
	p=${pbs[$pb]}
	if cmp --silent ./"$pb" "$p"
	then t=original
	else
		if cmp --silent ./"$pb" "$p".pacnew
		then t=' pacnew '
		else t=' merged '
		fi
	fi
	echo "[ $t ] $p"
	rm -f "$p".pacnew
	[[ "$t" = original ]] || cat ./"$pb" >"$p"
done

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