Merge pull request #2 from nathan-at-least/zcashd-use-latest-version-by-default

An empty `ZCASH_VERSION` (now default) installs latest `zcashd` release.

zcashd/Dockerfile

@@ -4,14 +4,24 @@ RUN apt-get update \
   && apt-get install -y gnupg2 apt-transport-https curl
 
 ARG ZCASH_SIGNING_KEY_ID=6DEF3BAF272766C0
-ARG ZCASH_VERSION=2.0.7+2
+
+ARG ZCASH_VERSION=
+# The empty string for ZCASH_VERSION will install the apt default version,
+# which should be the latest stable release. To install a specific
+# version, pass `--build-arg 'ZCASH_VERSION=<version>'` to `docker build`.
+
 ARG ZCASHD_USER=zcashd
 ARG ZCASHD_UID=2001
 
 RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys $ZCASH_SIGNING_KEY_ID \
   && echo "deb [arch=amd64] https://apt.z.cash/ jessie main" > /etc/apt/sources.list.d/zcash.list \
-  && apt-get update \
-  && apt-get install -y zcash=$ZCASH_VERSION
+  && apt-get update
+
+RUN if [ -z "$ZCASH_VERSION" ]; \
+    then apt-get install -y zcash; \
+    else apt-get install -y zcash=$ZCASH_VERSION; \
+    fi; \
+    zcashd --version
 
 RUN useradd --home-dir /srv/$ZCASHD_USER \
             --shell /bin/bash \