Add local whitelist to unblock entries

Signed-off-by: Knut Ahlers <knut@ahlers.me>

Dockerfile

@@ -5,6 +5,7 @@ WORKDIR /src
 
 RUN set -ex \
  && apk --no-cache add \
+      bash \
       curl \
       git \
       make \

Makefile

@@ -1,6 +1,4 @@
 default:
 
 blacklist:
-	curl -sSfL https://raw.githubusercontent.com/StevenBlack/hosts/master/hosts | awk '/^(#.*|0.0.0.0.*|)$$/' > blacklist
-	# Add local blacklist
-	cat blacklist.local >> blacklist
+	bash build_blacklist.sh

build_blacklist.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+set -euo pipefail
+
+target=blacklist
+
+# Download compiled blacklist
+curl -sSfL https://raw.githubusercontent.com/StevenBlack/hosts/master/hosts | awk '/^(#.*|0.0.0.0.*|)$$/' >${target}
+
+# Remove entries on local whitelist
+for entry in $(cat whitelist.local); do
+	grep -v "${entry}" ${target} >${target}.tmp
+	mv ${target}.tmp ${target}
+done
+
+# Add local blacklist
+cat blacklist.local >>${target}

whitelist.local

@@ -0,0 +1 @@
+app.pr0gramm.com