Updated documentation

README.md

@@ -54,6 +54,12 @@ pinned-package-updater update [Dockerfile, ...]
   - [ ] Red Hat Enterprise Linux 
     - (8, 9) are recognized by default, other versions may need additional configurations
   - [ ] Others with explicit configuration of package manager and default upstream repositories
+- [ ] Support external repositories added in the image manifest
+  - [ ] Support additional Alpine Linux repositories
+  - [ ] Support additional Debian repositories
+    - [ ] deb repositories
+    - [ ] ppa repositories
+  - [ ] Support additional Red Hat Linux repositories
 - [ ] Resolve pinned packages in Dockerfiles
   - [ ] Support for Alpine based images (apk)
   - [ ] Support for Debian based images (apt, apt-get)

test/data/old_pinned_dependencies_ubuntu.Dockerfile

@@ -1,7 +1,7 @@
 FROM ubuntu:18.04
 
 RUN echo "deb http://archive.canonical.com/ubuntu bionic partner" > /etc/apt/sources.list.d/partner.list \
-    && apt-get update && apt-get install \
+    && apt-get update && apt-get install -yq \
       ca-certificates=20210119~18.04.1 \
       curl=7.58.0-2ubuntu3.15 \
     && apt-get clean \