Postgres 12 is default; cleanup; polish comments

Author: NikolayS

extended/Dockerfile

@@ -1,11 +1,11 @@
-ARG PG_SERVER_VERSION=11
+ARG PG_SERVER_VERSION=12
 
 FROM postgres:${PG_SERVER_VERSION}
 LABEL maintainer="postgres.ai"
 
-
 ARG PG_SERVER_VERSION
 ENV PG_SERVER_VERSION=${PG_SERVER_VERSION:-12}
+
 ENV CITUS_VERSION=9.4
 
 RUN apt-get clean && rm -rf /var/lib/apt/lists/partial \
@@ -20,25 +20,24 @@ RUN apt-get clean && rm -rf /var/lib/apt/lists/partial \
     && apt-get install --no-install-recommends -y \
        postgresql-${PG_SERVER_VERSION}-hypopg \
     && apt-get install --no-install-recommends -y \
-       postgresql-${PG_SERVER_VERSION}-hypopg-dbgsym \ 
-    # pg_hint_plan extension  (convert versions with dot "9.6" to "96")
+       postgresql-${PG_SERVER_VERSION}-hypopg-dbgsym \
+    # pg_hint_plan extension (dots are to be skipped here, e.g., "9.6" -> "96")
     && export PG_PLAN_HINT_VERSION=$(echo $PG_SERVER_VERSION | sed 's/\.//') \
       && wget --quiet -O /tmp/pg_hint_plan.zip \
          https://github.com/ossc-db/pg_hint_plan/archive/PG${PG_PLAN_HINT_VERSION}.zip \
       && unzip /tmp/pg_hint_plan.zip -d /tmp \
          && cd /tmp/pg_hint_plan-PG${PG_PLAN_HINT_VERSION} \
       && make && make install \
    # timescaledb extension
-   && echo 'deb https://packagecloud.io/timescale/timescaledb/debian/' \ 
-      $(env -i bash -c '. /etc/os-release; echo ${VERSION_CODENAME}') \ 
+   && echo 'deb https://packagecloud.io/timescale/timescaledb/debian/' \
+      $(env -i bash -c '. /etc/os-release; echo ${VERSION_CODENAME}') \
       'main' > /etc/apt/sources.list.d/timescaledb.list \
       && wget --quiet -O - \
          https://packagecloud.io/timescale/timescaledb/gpgkey | sudo apt-key add - \
       && apt-get update \
       && apt-get install -y timescaledb-postgresql-${PG_SERVER_VERSION} \
-   # citus extension. 11 and 12 versions only  are supported by citus 
+   # citus extension; only Postgres 11 and 12 are supported by citus
    && if [ "${PG_SERVER_VERSION}" = "12" ] || [ "${PG_SERVER_VERSION}" = "11" ]; then \
-      # only 11 and 12 versions are supported by citus
       curl -s https://install.citusdata.com/community/deb.sh | bash \
       && apt-get install -y postgresql-${PG_SERVER_VERSION}-citus-${CITUS_VERSION} \
          postgresql-${PG_SERVER_VERSION}-hll=2.14.citus-1 \
@@ -56,21 +55,21 @@ RUN apt-get clean && rm -rf /var/lib/apt/lists/partial \
      && export USE_PGXS=1 && make && make install && cd .. && rm -rf pg_show_plans \
    # pg_cron extension
    && apt-get install -y postgresql-${PG_SERVER_VERSION}-cron \
-   # postgresql_anonymizer extension 
+   # postgresql_anonymizer extension
    && pgxn install ddlx && pgxn install postgresql_anonymizer \
    # pg_stat_kcache extension
    && apt-get install postgresql-${PG_SERVER_VERSION}-pg-stat-kcache \
    # add pg_qualstats extension
    && apt-get install postgresql-${PG_SERVER_VERSION}-pg-qualstats \
    # pg_mon extension
-   && git clone https://github.com/CyberDem0n/bg_mon.git && cd bg_mon \ 
+   && git clone https://github.com/CyberDem0n/bg_mon.git && cd bg_mon \
      && USE_PGXS=1 make && USE_PGXS=1 make install \
    # pgextwlist extension
    && apt-get install postgresql-${PG_SERVER_VERSION}-pgextwlist \
    # pg_auth_mon extension
    && git clone https://github.com/RafiaSabih/pg_auth_mon.git \
      && cd pg_auth_mon && USE_PGXS=1 make && USE_PGXS=1 make install \
-   #  set_user extension
+   # set_user extension
    && git clone https://github.com/pgaudit/set_user.git \
      && cd set_user && make USE_PGXS=1 && make USE_PGXS=1 install \
    # remove all auxilary packages to reduce final image size
@@ -81,18 +80,18 @@ RUN apt-get clean && rm -rf /var/lib/apt/lists/partial \
       libgssrpc4 libkadm5clnt-mit11 libkadm5srv-mit11 \
      && apt-get clean -y autoclean \
      && rm -rf /var/lib/apt/lists/* \
-   # remove standard pgdata 
-   && rm -rf /var/lib/postgresql/${PG_SERVER_VERSION}/ 
+   # remove standard pgdata
+   && rm -rf /var/lib/postgresql/${PG_SERVER_VERSION}/
 
 EXPOSE 5432
 
-# Prepare Postgres start script.
+# Prepare Postgres start script
 RUN echo "#!/bin/bash" > /pg_start.sh && chmod a+x /pg_start.sh \
     && echo "chown -R postgres:postgres /var/lib/postgresql/pgdata /var/run/postgresql" \
       >> /pg_start.sh \
     && printf "sudo -u postgres /usr/lib/postgresql/${PG_SERVER_VERSION}/bin/postgres -D /var/lib/postgresql/pgdata \n" \
       >> /pg_start.sh \
-    # Infinite sleep to allow restarting Postgres.
+    # Infinite sleep to allow restarting Postgres
     && echo "/bin/bash -c \"trap : TERM INT; sleep infinity & wait\"" \
       >> /pg_start.sh