Use the entrypoint setup to run jekyll

Dockerfile

@@ -10,4 +10,4 @@ RUN bundle config --global frozen 1
 
 RUN bundle install
 
-CMD ["jekyll", "serve", "--trace"]
+ENTRYPOINT ["/sbin/entrypoint.sh"]

sbin/entrypoint.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+
+set -eu -o pipefail
+
+# Fire up Jekyll with the right configuration
+run_jekyll() {
+  set -eu
+
+  jekyll serve \
+    --port "$JEKYLL_PORT" \
+    --host "$JEKYLL_HOST" \
+    --ssl-cert "$JEKYLL_SSL_CERT" \
+    --ssl-key "$JEKYLL_SSL_KEY" \
+    --trace
+}
+
+# Main entrypoint
+main() {
+  set -eu
+
+  run_jekyll
+}
+
+main