=== modified file 'common.zsh'
--- common.zsh	2017-12-13 00:54:25 +0000
+++ common.zsh	2017-12-13 00:49:11 +0000
@@ -34,7 +34,7 @@
 
 # Logical variable handling
 ground() {
-	(($# == 1)) || die "usage: $0 <variable>"
+	(($# == 1)) || die
 	(($+vals[$vars[$1]]))
 }
 
@@ -57,7 +57,7 @@
 }
 
 setvar() {
-	(($# == 2)) || die "usage: $0 <variable> <value>"
+	(($# == 2)) || die
 	if ground $1; then
 		[[ $vals[$vars[$1]] == $2 ]] \
 			|| die "$0: Could not unify $1 (value ${(qqq)vals[$vars[$1]]}) with ${(qqq)2}"
@@ -74,7 +74,7 @@
 }
 
 fresh() {
-	(($# < 2)) || die "usage: $0 [<variable>]"
+	(($# < 2)) || die
 	value_counter=$[value_counter + 1]
 	last_var=${1:-_$value_counter}
 	(($+vars[$last_var])) && die "$0: Variable already defined: $1"
@@ -90,7 +90,7 @@
 }
 
 unify() {
-	(($# == 2)) || die "usage: $0 <variable1> <variable2>"
+	(($# == 2)) || die
 	if ground $1; then
 		if ground $2; then
 			[[ $vals[$vars[$1]] == $vals[$vars[$2]] ]] \
@@ -203,9 +203,9 @@
 
 # dependency tracking
 dep_add_file() {
-	(($# < 2)) || die "usage: $0 <filename> [<variable>]"
+	(($# > 2)) || die
 	local out
-	out=$(sha256sum $1) || die "$0: Unable to checksum: ${(qqq)1}"
+	out=$(sha256sum $1) || die
 	__check_deps__+='if { test -e '${(qqq)1}$' }\n'
 	__check_deps__+='if { pipeline -d { printf "%s\n" '${(qqq)out}$' } sha256sum -c }\n'
 	(($# == 2)) && setvar $2 ${out%% *}
@@ -227,7 +227,7 @@
 }
 
 dep_add_dir() {
-	(($# < 2)) || die "usage: $0 <filename> [<variable>]"
+	(($# > 2)) || die
 	[[ -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 -)
@@ -238,7 +238,7 @@
 }
 
 dep_add_dir_mtimes() {
-	(($# < 2)) || die "usage: $0 <filename> [<variable>]"
+	(($# > 2)) || die
 	[[ -d $1 ]] || die "$0: ${(qqq)1} does not exist or not a directory"
 	local out
 	out=$(tar -cvp -C $1 . | sha256sum -)