=== modified file 'common.zsh'
--- common.zsh	2017-12-12 17:03:06 +0000
+++ common.zsh	2017-12-12 10:33:38 +0000
@@ -8,16 +8,15 @@
 OUT=$3
 FUNCDIR=${0:h:a}/functions
 TARGET=${BASE##*/}.${${${DO:t}%.do}#default.}
-typeset -ga finish_hooks
 
 # helper that prints out error message and exits
 die() {
-	print -r - "$fg_bold[red]* $fg[cyan]${${${DO:t}%.do}#default.}:$reset_color $@" >&2
+	print -r - "$fg_bold[red]*$reset_color $@" >&2
 	exit 1
 }
 
 info() {
-	print -r - "$fg_bold[green]* $fg[cyan]${${${DO:t}%.do}#default.}:$reset_color $@" >&2
+	print -r - "$fg_bold[green]*$reset_color $@" >&2
 }
 
 autoload_functions() {
@@ -72,17 +71,6 @@
 	info "entering: $name $(decode_argstr)"
 }
 
-add_finish_hook() {
-	finish_hooks+=( ${(pj:\0:)@} )
-}
-
-run_finish_hooks() {
-	local hook
-	for hook in "$finish_hooks[@]"; do
-		"${(0@)hook}" || die "Hook failed: ${(0)hook}"
-	done
-}
-
 finish-info(){
 	local name
 	name=${${${DO:t}%.do}#default.}
@@ -93,7 +81,6 @@
 }
 
 finish() {
-	run_finish_hooks
 	finish-info
 	print-meta >$OUT
 	exit 0
@@ -118,52 +105,19 @@
 	(( $#empty )) && die "required parameters are empty: ${(@q)empty}"
 }
 
-dep_add_file() {
-	local out
-	out=$(sha256sum $1) || die
-	vars[__check_deps__]+='if { test -e '${(qqq)1}$' }\n'
-	vars[__check_deps__]+='if { pipeline -d { printf "%s\n" '${(qqq)out}$' } sha256sum -c }\n'
-}
-
-dep_add_missing() {
-	[[ -e $1 ]] || die "$0: ${(qqq)1} exists"
-	vars[__check_deps__]+='if -n { test -e '${(qqq)1}$' }\n'
-}
-
-dep_add_file_or_missing() {
+filehash() {
 	if [[ -f $1 ]]; then
-		dep_add_file $1
-	elif [[ -e $1 ]]; then
-		die "$0: ${(qqq)1} exists and is not a file"
+		sha256sum $1
 	else
-		dep_add_missing
+		printf '-  %s\n' $1
 	fi
 }
 
-dep_add_dir() {
-	[[ -d $1 ]] || die "$0: ${(qqq)1} does not exist or not a directory"
-	local out
-	out=$(tar -cvp -C $1 --mtime=1970-01-01 . | sha256sum -)
-	(( ${(j.|.)pipestatus} )) \
-		&& die "$0: Failed to checksum directory: ${(qqq)1}"
-	vars[__check_deps__]+='if { pipeline -d { printf "%s\n" '${(qqq)out}'} fdmove 3 1 pipeline -d { tar -cvp --mtime=1970-01-01 -C '${(qqq)1}$' . } sha256sum -c /proc/self/fd/3 }\n'
-}
-
-dep_add_dir_mtimes() {
-	[[ -d $1 ]] || die "$0: ${(qqq)1} does not exist or not a directory"
-	local out
-	out=$(tar -cvp -C $1 . | sha256sum -)
-	(( ${(j.|.)pipestatus} )) \
-		&& die "$0: Failed to checksum directory: ${(qqq)1}"
-	vars[__check_deps__]+='if { pipeline -d { printf "%s\n" '${(qqq)out}'} fdmove 3 1 pipeline -d { tar -cvp -C '${(qqq)1}$' . } sha256sum -c /proc/self/fd/3 }\n'
-}
-
 ifchange() {
 	local arg
 	redo-ifchange "$@" || die "failed to build one or more dependencies: $*"
 	for arg in "$@"; do
-		vars[__check_deps__]+='if { redo-ifchange '${(qqq)arg}$' }\n'
-		dep_add_file $arg
+		vars[__deps__]+=$'\n'$(filehash $arg)
 	done
 }
 
@@ -183,10 +137,10 @@
 
 	for arg in "${(s::Q)$(<$FILE)}"; do
 		if [[ "$arg" != *=* ]]; then
-			die "$0: Malformed argument: ${(qqq)arg}"
+			die "Malformed argument: ${(qqq)arg}"
 		fi
 		if (( $+previous[${arg%%=*}] )); then
-			die "$0: Duplicate argument: ${arg%%=*}"
+			die "Duplicate argument: ${arg%%=*}"
 		fi
 		previous[${arg%%=*}]=${arg#*=}
 	done
@@ -195,12 +149,59 @@
 	has_previous=1
 }
 
+is-unchanged() {
+	local arg
+
+	parse-previous
+
+	if [[ "${(ko)vars}" != "${(ko)previous}" ]]; then
+		info "changed: different variables"
+		info "now: ${(ko)vars}"
+		info "was: ${(ko)previous}"
+		return 2
+	fi
+
+	for arg in ${(k)vars}; do
+		if [[ $arg == __deps__ ]]; then
+			local line
+			for line in ${(f)${previous[$arg]}}; do
+				if [[ $line == '-  '* ]]; then
+					if [[ -e $line[4,-1] ]]; then
+						info "changed: file exists: ${(qqq)line[4,-1]}"
+						return 4
+					fi
+				else
+					if ! sha256sum -c <<<$line; then
+						info "changed: file changed: ${(qqq)line#*  }"
+						return 5
+					fi
+				fi
+			done
+		elif [[ $vars[$arg] != $previous[$arg] ]]; then
+			info "changed: variable $arg"
+			info "now: ${(qqq)vars[$arg]}"
+			info "was: ${(qqq)previous[$arg]}"
+			return 3
+		fi
+	done
+	return 0
+}
+
 exit-unchanged() {
 	info "$DO:t unchanged, skipping build"
 	cp $FILE $OUT
 	exit 0
 }
 
+exit-if-unchanged() {
+	if is-unchanged; then
+		exit-unchanged
+	else
+		print-meta > $FILE.new
+		[[ -f $FILE ]] && cp $FILE $FILE.prev
+	fi
+}
+
 depend() {
 	# TODO: edit this comment copied over from confz
 	# usage: require <name> [<variables>] [-- <arguments>]
@@ -281,12 +282,7 @@
 	autoload_functions
 	decode_args
 	start-info
-	dep_add_file $DO
-	dep_add_file common.zsh
-	parse-previous
-	if (($+previous[__check_deps__])) && execlineb -c $previous[__check_deps__]; then
-		exit-unchanged
-	fi
+	vars[__deps__]=$(sha256sum $DO common.zsh)
 	main || exit $?
 	finish
 fi

=== modified file 'functions/clone-build-dir'
--- functions/clone-build-dir	2017-12-12 17:03:06 +0000
+++ functions/clone-build-dir	2017-11-30 21:40:46 +0000
@@ -1,4 +1,3 @@
-init-build-dir-vars
 while grep -q "^overlay ${vars[build_dir]:A} overlay" /proc/mounts; do
 	umount ${vars[build_dir]:A} || die "Failed to umount ${(qqq)vars[build_dir]}"
 done

=== added file 'functions/hash-build-dir'
--- functions/hash-build-dir	1970-01-01 00:00:00 +0000
+++ functions/hash-build-dir	2017-11-30 21:49:11 +0000
@@ -0,0 +1,9 @@
+if [[ -d $vars[build_dir] ]]; then
+	local sum
+	sum=$(pax -w $vars[build_dir] | sha256sum -) \
+		|| die "Failed to checksum build directory ${(qqq)vars[build_dir]}"
+	vars[sha256sum]=${sum%% *}
+else
+	vars[sha256sum]=-
+fi
+# vim: fileencoding=utf8 ft=zsh noet sw=4 ts=4 sts=4

=== added file 'functions/hash-build-files'
--- functions/hash-build-files	1970-01-01 00:00:00 +0000
+++ functions/hash-build-files	2017-11-30 21:49:11 +0000
@@ -0,0 +1,9 @@
+if [[ -d $vars[build_dir] ]]; then
+	local sum
+	sum=$(sha256sum $vars[build_dir]/**/*(.D) | sha256sum -) \
+		|| die "Failed to checksum files in build directory ${(qqq)vars[build_dir]}"
+	vars[sha256sum]=${sum%% *}
+else
+	vars[sha256sum]=-
+fi
+# vim: fileencoding=utf8 ft=zsh noet sw=4 ts=4 sts=4

=== added file 'functions/hash-changes'
--- functions/hash-changes	1970-01-01 00:00:00 +0000
+++ functions/hash-changes	2017-11-30 21:40:46 +0000
@@ -0,0 +1,9 @@
+if [[ -d $vars[changes_dir] ]]; then
+	local sum
+	sum=$(pax -w $vars[changes_dir] | sha256sum -) \
+		|| die "Failed to checksum changes directory ${(qqq)vars[changes_dir]}"
+	vars[sha256sum]=${sum%% *}
+else
+	vars[sha256sum]=-
+fi
+# vim: fileencoding=utf8 ft=zsh noet sw=4 ts=4 sts=4

=== removed file 'functions/output-dir'
--- functions/output-dir	2017-12-12 17:03:06 +0000
+++ functions/output-dir	1970-01-01 00:00:00 +0000
@@ -1,14 +0,0 @@
-while grep -q "^[^ ]\\+ ${1:A} " /proc/mounts; do
-	umount ${1:A} || die "$0: Failed to umount ${(qqq)1}"
-done
-
-local -a remove
-[[ -e $1 ]] && remove+=( $1/*(DN) )
-if (($#remove)); then
-	rm -rf $remove || die "$0: Failed to clean output directory: ${(qqq)1}"
-fi
-
-mkdir -p $1 || die "Failed to create output directory: ${(qqq)1}"
-
-add_finish_hook dep_add_dir $1
-# vim: fileencoding=utf8 ft=zsh noet sw=4 ts=4 sts=4