ci: add Drone CI

This is my first experiment to make sure I can actually use this in my
CI.

.drone.yml

@@ -6,7 +6,7 @@ name: Matrix Notifier check
 steps:
 - name: Pre-commit checks
   commands:
-  - nix flake check -vvv
+  - nix flake check
 
 - name: Notifiy
   commands:
@@ -20,9 +20,6 @@ steps:
       from_secret: matrix_username
     PASS:
       from_secret: matrix_password
-    MESSAGE:
-      # FIXME: need to find a way to link
-      "Build ${DRONE_BUILD_STATUS} [${DRONE_REPO_OWNER}/${DRONE_REPO_NAME}](${dummy_link}) (${DRONE_BRANCH}) by ${DRONE_COMMIT_AUTHOR}"
   settings:
     trigger:
       status:

matrix-notifier

@@ -23,6 +23,17 @@ rawurlencode() {
     echo "$encoded")
 }
 
+default_drone_message() {
+    local msg="Build ${DRONE_BUILD_STATUS}"
+    msg="$msg ${DRONE_REPO_OWNER}/${DRONE_REPO_NAME}/${DRONE_BUILD_NUMBER}"
+    msg="$msg (${DRONE_BRANCH})"
+    printf '%s' "$msg"
+}
+
+if [ "$DRONE" == "true" ] && [ -z "$MESSAGE" ]; then
+    MESSAGE="$(default_drone_message)"
+fi
+
 if [ -z "$USER" ] || [ -z "$PASS" ]; then
     print_err "You must provide USER and PASS"
     exit 1