Add Alpine variant to 1.6

1.6-rc/alpine3.13/Dockerfile

@@ -0,0 +1,48 @@
+FROM alpine:3.13
+
+ENV JULIA_PATH /usr/local/julia
+ENV PATH $JULIA_PATH/bin:$PATH
+
+# https://julialang.org/juliareleases.asc
+# Julia (Binary signing key) <[email protected]>
+ENV JULIA_GPG 3673DF529D9049477F76B37566E3C7DC03D6E495
+
+# https://julialang.org/downloads/
+ENV JULIA_VERSION 1.6.0-rc2
+
+RUN set -eux; \
+	\
+	apk add --no-cache --virtual .fetch-deps gnupg; \
+	\
+# https://julialang.org/downloads/#julia-command-line-version
+# https://julialang-s3.julialang.org/bin/checksums/julia-1.6.0-rc2.sha256
+# this "case" statement is generated via "update.sh"
+	apkArch="$(apk --print-arch)"; \
+	case "$apkArch" in \
+# amd64
+		x86_64) tarArch='x86_64'; dirArch='x64'; sha256='8c04675221c6494ada41cb5c1abe08ff18703626b6fd7161132cd56324913f8e' ;; \
+		*) echo >&2 "error: current architecture ($apkArch) does not have a corresponding Julia binary release"; exit 1 ;; \
+	esac; \
+	\
+	folder="$(echo "$JULIA_VERSION" | cut -d. -f1-2)"; \
+	wget -O julia.tar.gz.asc "https://julialang-s3.julialang.org/bin/musl/${dirArch}/${folder}/julia-${JULIA_VERSION}-musl-${tarArch}.tar.gz.asc"; \
+	wget -O julia.tar.gz     "https://julialang-s3.julialang.org/bin/musl/${dirArch}/${folder}/julia-${JULIA_VERSION}-musl-${tarArch}.tar.gz"; \
+	\
+	echo "${sha256} *julia.tar.gz" | sha256sum -c -; \
+	\
+	export GNUPGHOME="$(mktemp -d)"; \
+	gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys "$JULIA_GPG"; \
+	gpg --batch --verify julia.tar.gz.asc julia.tar.gz; \
+	command -v gpgconf > /dev/null && gpgconf --kill all; \
+	rm -rf "$GNUPGHOME" julia.tar.gz.asc; \
+	\
+	mkdir "$JULIA_PATH"; \
+	tar -xzf julia.tar.gz -C "$JULIA_PATH" --strip-components 1; \
+	rm julia.tar.gz; \
+	\
+	apk del --no-network .fetch-deps; \
+	\
+# smoke test
+	julia --version
+
+CMD ["julia"]