Updates go, ruby, alpine and components

Dockerfile

@@ -1,7 +1,7 @@
 # Build caddy from source, because binaries are published under a commercial license: https://caddyserver.com/pricing
 # Starting with 1.0.0 we seem to no longer have to do this:  https://github.com/mholt/caddy/releases/tag/v1.0.0
 # OTOH - with explicit plugin versions the build remains more deterministic than downloading the "latest" plugins via https://caddyserver.com/download
-FROM golang:1.12.4 as caddybuild
+FROM golang:1.12.8 as caddybuild
 
 # https://github.com/mholt/caddy/releases
 ARG CADDY_VERSION="v1.0.3"
@@ -31,13 +31,14 @@ RUN cp caddy /dist/usr/local/bin/
 
 
 # Declare common ruby base image for all ruby-stages
-FROM ruby:2.6.2-alpine3.9 as gollum-ruby
+FROM ruby:2.6.3-alpine3.10 as gollum-ruby
 
 
 FROM gollum-ruby as gollum-build
 
+# See e.g. https://pkgs.alpinelinux.org/packages?name=icu-dev&branch=v3.10
 ARG ALPINE_SDK_VERSION=1.0-r0
-ARG ICU_DEV_VERSION=62.1-r0
+ARG ICU_DEV_VERSION=64.2-r0
 ARG GOLLUM_VERSION=4.1.4
 
 COPY --from=caddybuild --chown=1000:1000 /dist /dist
@@ -76,8 +77,9 @@ ARG SOURCE_REPOSITORY_URL
 ARG GIT_TAG
 ARG BUILD_DATE
 # - Sources:
-#   - https://pkgs.alpinelinux.org/packages?name=git&branch=v3.9
-ARG GIT_VERSION=2.20.1-r0
+#   - https://pkgs.alpinelinux.org/packages?name=git&branch=v3.10
+ARG GIT_VERSION=2.22.0-r0
+ARG LIBCAP_VERSION=2.27-r0
 
 # See https://github.com/opencontainers/image-spec/blob/master/annotations.md
 LABEL org.opencontainers.image.created="${BUILD_DATE}" \
@@ -109,7 +111,7 @@ RUN \
   # Needed for running gollum
   && apk --update add git=$GIT_VERSION \
   # Needed for setcap
-  libcap=2.26-r0 \
+  libcap=$LIBCAP_VERSION \
   # cleanup apk cache
   && rm -rf /var/cache/apk/* \
   # Initialize wiki data.