add shed utility to apply sed more intelligently

notwa-util/Dockerfile

@@ -3,7 +3,7 @@
 FROM alpine:3.16 as partial
 # need this for acquire (.tar.xz files):
 RUN apk add --no-cache xz
-COPY --chmod=0755 acquire cosmocc dedupe quickconf \
+COPY --chmod=0755 acquire cosmocc dedupe quickconf shed \
     /usr/local/bin/
 
 FROM partial as downloader

notwa-util/shed

@@ -0,0 +1,11 @@
+#!/usr/bin/env sh
+: \
+ && f="${1?missing filename}" && shift \
+ &&  for e in "$@" \
+    ;do : \
+     && cp "$f" "$f.bak" && sed -i -e "$e" "$f" \
+     && { diff -q "$f" "$f.bak" >/dev/null; [ $? = 1 ] ;} \
+     || { printf >&2 '\033[91mfailed to apply sed:\033[m\n%s\n' "$e"; exit 1 ;} \
+     && rm "$f.bak" || exit \
+    ;done \
+;