works!!!!!

.dockerignore

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+.git
+.github

src/core-release-filter.jq

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+[
+  .assets[]
+  | . as $release
+  | if (.name | test("dhall-[0-9.]+.*-linux.tar.bz2"; "i")) then
+    $release.browser_download_url
+  else
+    ""
+  end
+ ] | reduce .[] as $url (""; . + $url)

src/entrypoint.sh

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+#!/bin/sh
+set -e
+
+apk add --quiet --no-progress curl jq
+
+echo "Installing dhall version: $1"
+
+url_path=latest
+
+if [ "$1" != "latest" ]
+then
+  url_path="tags/$1"
+fi
+
+curl -s https://api.github.com/repos/dhall-lang/dhall-haskell/releases/$url_path > releases.json
+
+core_download_url=$(jq --from-file src/core-release-filter.jq releases.json | tr -d '"')
+json_download_url=$(jq --from-file src/json-release-filter.jq releases.json | tr -d '"')
+
+# Cleanup to make sure the download can't fail
+rm -f releases.json
+rm -f dhall-*
+
+echo "Downloading dhall from: $core_download_url"
+wget --quiet $core_download_url
+
+echo "Downloading dhall-json from: $json_download_url"
+wget --quiet $json_download_url
+
+# Extract dhall-json first, makes shell glob easier
+tar --extract --bzip2 --file dhall-json-*-linux.tar.bz2
+rm -f dhall-json-*-linux.tar.bz2
+
+# Extract dhall now that dhall-json is done
+tar --extract --bzip2 --file dhall-*-linux.tar.bz2
+rm -f dhall-*-linux.tar.bz2
+
+# Add the dhall executables to the path for future actions
+echo "::add-path::$(pwd)/bin"

src/json-release-filter.jq

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+[
+  .assets[]
+  | . as $release
+  | if (.name | test("dhall-json-[0-9.]+.*-linux.tar.bz2"; "i")) then
+    $release.browser_download_url
+  else
+    ""
+  end
+ ] | reduce .[] as $url (""; . + $url)