Optimize docker image as suggested in #97

.travis.yml

@@ -5,10 +5,10 @@ os:
   - osx
 
 rvm:
-  - ruby-head
-  - 2.7
-  - 2.5
-  - 2.1
+  - 2.7 # Current stable
+  - 2.6 # Alpine 3.11
+  - 2.5 # Debian stable (buster), Ubuntu
+  - 2.1 # Minimum supported version (Debian oldoldstable (jessie))
 
 matrix:
   fast_finish: true

Dockerfile

@@ -2,24 +2,22 @@
 # docker build -t transmission-rss --build-arg UID=1337 --build-arg GID=1337 .
 # docker run -it -v $(pwd)/transmission-rss.conf:/etc/transmission-rss.conf transmission-rss
 
-FROM ruby:alpine
-MAINTAINER henning mueller <[email protected]>
+FROM alpine:3 as builder
+RUN apk add gcc libc-dev make ruby-dev
+COPY . /tmp
+WORKDIR /tmp
+RUN \
+  gem build transmission-rss.gemspec && \
+  gem install -N --build-root /build transmission-rss-*.gem
 
+FROM alpine:3
+MAINTAINER henning mueller <[email protected]>
 ARG UID=1000
 ARG GID=1000
-
 RUN \
   addgroup -g $GID ruby && \
   adduser -u $UID -G ruby -D ruby && \
-  apk --no-cache --update add build-base libffi-dev
-
-WORKDIR home/ruby
-COPY . transmission-rss
-RUN chown -R ruby:ruby transmission-rss
-
+  apk add --no-cache ruby ruby-etc ruby-json
 USER ruby
-
-WORKDIR transmission-rss
-RUN bundle
-
-CMD bundle exec ./bin/transmission-rss
+COPY --from=builder /build /
+CMD ["transmission-rss"]

bin/transmission-rss

@@ -133,7 +133,8 @@ unless config.privileges.empty?
     ':' +
     config.privileges.group
 else
-  log.debug('no privilege dropping')
+  user = Etc.getpwuid(Process.euid).name
+  log.debug('no privilege dropping, running as user ' + user)
 end
 
 # Warn if no feeds are given.