Fix log output by using a proble matcher instead (#23)

src/Dockerfile

@@ -14,5 +14,6 @@ RUN \
 SHELL ["/bin/bash", "-o", "pipefail", "-c"]
 
 COPY entrypoint.sh /entrypoint.sh
+COPY matcher.json /matcher.json
 
 ENTRYPOINT ["/entrypoint.sh"]

src/entrypoint.sh

@@ -1,8 +1,14 @@
 #!/usr/bin/env bash
 declare -a options
 
-# This is a GitHub Action... Act like it :)
-options+=(--format github)
+# Use standard formatting, the GitHub Action annotation is nice, but
+# hides information from the logs. This action uses standard output
+# with a problem matcher instead.
+options+=(--format standard)
+
+# Register problem matcher
+cp /matcher.json "${PWD}/matcher.json"
+echo "::add-matcher::matcher.json"
 
 # Custom path for yamllint configuration input
 if [[ -n "${INPUT_CONFIG}" ]]; then

src/matcher.json

@@ -0,0 +1,22 @@
+{
+  "problemMatcher": [
+    {
+      "owner": "yamllint",
+      "pattern": [
+        {
+          "regexp": "^(.*\\.ya?ml)$",
+          "file": 1
+        },
+        {
+          "regexp": "^\\s{2}(\\d+):(\\d+)\\s+(error|warning)\\s+(.*?)\\s+\\((.*)\\)$",
+          "line": 1,
+          "column": 2,
+          "severity": 3,
+          "message": 4,
+          "code": 5,
+          "loop": true
+        }
+      ]
+    }
+  ]
+}