Merge branch 'muslstack' into 'registry'

Workaround for segmentation faults in hugo_extended registry image

See merge request pages/hugo!86

Dockerfile

-FROM alpine:latest
+# Dockerfile for Hugo (HUGO=hugo) / Hugo Extended (HUGO=hugo_extended)
+# HUGO_VERSION / HUGO_SHA / HUGO_EXTENDED_SHA is automatically updated
+# by update.py when new release is available on the upstream.
+# Utilize multi-stage builds to make images optimized in size.
 
+# First stage - download prebuilt hugo binary from the GitHub release.
+# Use golang image to run https://github.com/yaegashi/muslstack
+# on hugo executable to extend its default thread stack size to 8MB
+# to work around segmentation fault issues.
+FROM golang:1.12-alpine
 ARG HUGO=hugo
 ARG HUGO_VERSION=0.55.6
-ARG HUGO_APK="ca-certificates openssl git"
 ARG HUGO_SHA=39d3119cdb9ba5d6f1f1b43693e707937ce851791a2ea8d28003f49927c428f4
-ARG HUGO_EXTENDED_APK="libc6-compat libstdc++"
 ARG HUGO_EXTENDED_SHA=8962b8cdc0ca220da97293cea0bb1b31718cb4d99d0766be6865cb976b1c1805
-
-# Install HUGO
 RUN set -eux && \
     case ${HUGO} in \
       *_extended) \
-        HUGO_APK="${HUGO_APK} ${HUGO_EXTENDED_APK}" \
         HUGO_SHA="${HUGO_EXTENDED_SHA}" ;; \
     esac && \
-    apk add --update --no-cache ${HUGO_APK} && \
-  wget -O ${HUGO_VERSION}.tar.gz https://github.com/spf13/hugo/releases/download/v${HUGO_VERSION}/${HUGO}_${HUGO_VERSION}_Linux-64bit.tar.gz && \
-  echo "${HUGO_SHA}  ${HUGO_VERSION}.tar.gz" | sha256sum -c && \
-  tar xf ${HUGO_VERSION}.tar.gz && mv hugo* /usr/bin/hugo && \
-  rm -rf  ${HUGO_VERSION}.tar.gz && \
-  rm -rf /var/cache/apk/* && \
-  hugo version
+    apk add --update --no-cache ca-certificates openssl git && \
+    wget -O ${HUGO_VERSION}.tar.gz https://github.com/spf13/hugo/releases/download/v${HUGO_VERSION}/${HUGO}_${HUGO_VERSION}_Linux-64bit.tar.gz && \
+    echo "${HUGO_SHA}  ${HUGO_VERSION}.tar.gz" | sha256sum -c && \
+    tar xf ${HUGO_VERSION}.tar.gz && mv hugo* /usr/bin/hugo
+RUN go get github.com/yaegashi/muslstack
+RUN muslstack -s 0x800000 /usr/bin/hugo
 
+# Second stage - build the final image with minimal apk dependencies.
+# alpine:edge is required for muslstack to work as of June 2019.
+FROM alpine:edge
+ARG HUGO=hugo
+COPY --from=0 /usr/bin/hugo /usr/bin
+RUN set -eux && \
+    case ${HUGO} in \
+      *_extended) \
+        apk add --update --no-cache libc6-compat libstdc++ && \
+        rm -rf /var/cache/apk/* ;; \
+    esac && \
+    hugo version
 EXPOSE 1313
-
+WORKDIR /src
 CMD ["/usr/bin/hugo"]