feat: Bake build metadata (git tag, commit, date) into OCI image and display in web UI

Store git tag, commit hash, and build date as OCI-standard labels and a
build_meta.json file inside the Docker image. The Flask app reads this at
startup and displays version info in all page footers. Adds /version JSON
endpoint for programmatic access. Falls back to dev@local outside Docker.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Makefile

@@ -45,7 +45,11 @@ web-debug: $(PYTHON)
 	FLASK_DEBUG=1 $(PYTHON) app.py
 
 image:
-	docker build -t fuj-management:latest -f build/Dockerfile .
+	docker build -t fuj-management:latest \
+		--build-arg GIT_TAG=$$(git describe --tags --always 2>/dev/null || echo "untagged") \
+		--build-arg GIT_COMMIT=$$(git rev-parse --short HEAD) \
+		--build-arg BUILD_DATE=$$(date -u +%Y-%m-%dT%H:%M:%SZ) \
+		-f build/Dockerfile .
 
 run:
 	docker run -it --rm -p 5001:5001 -v $(CURDIR)/.secret:/app/.secret:ro fuj-management:latest

app.py

@@ -72,6 +72,13 @@ def warmup_cache():
     logger.info("Cache warmup complete.")
 
 app = Flask(__name__)
+
+import json as _json
+_meta_path = Path(__file__).parent / "build_meta.json"
+BUILD_META = _json.loads(_meta_path.read_text()) if _meta_path.exists() else {
+    "tag": "dev", "commit": "local", "build_date": ""
+}
+
 warmup_cache()
 
 @app.before_request
@@ -101,7 +108,7 @@ def inject_render_time():
             "total": f"{total:.3f}",
             "breakdown": " | ".join(breakdown)
         }
-    return dict(get_render_time=get_render_time)
+    return dict(get_render_time=get_render_time, build_meta=BUILD_META)
 
 @app.route("/")
 def index():
@@ -113,6 +120,10 @@ def flush_cache_endpoint():
     deleted = flush_cache()
     return jsonify({"status": "ok", "deleted_files": deleted})
 
+@app.route("/version")
+def version():
+    return BUILD_META
+
 @app.route("/fees")
 def fees():
     attendance_url = f"https://docs.google.com/spreadsheets/d/{ATTENDANCE_SHEET_ID}/edit"

build/Dockerfile

@@ -24,6 +24,17 @@ COPY templates/ ./templates/
 COPY build/entrypoint.sh /entrypoint.sh
 RUN chmod +x /entrypoint.sh
 
+ARG GIT_TAG=unknown
+ARG GIT_COMMIT=unknown
+ARG BUILD_DATE=unknown
+
+LABEL org.opencontainers.image.version="${GIT_TAG}" \
+      org.opencontainers.image.revision="${GIT_COMMIT}" \
+      org.opencontainers.image.created="${BUILD_DATE}" \
+      org.opencontainers.image.title="fuj-management"
+
+RUN echo "{\"tag\": \"${GIT_TAG}\", \"commit\": \"${GIT_COMMIT}\", \"build_date\": \"${BUILD_DATE}\"}" > /app/build_meta.json
+
 EXPOSE 5001
 
 HEALTHCHECK --interval=60s --timeout=5s --start-period=5s \

templates/adults.html

@@ -647,7 +647,7 @@
     {% set rt = get_render_time() %}
     <div class="footer"
         onclick="document.getElementById('perf-details').style.display = (document.getElementById('perf-details').style.display === 'block' ? 'none' : 'block')">
-        render time: {{ rt.total }}s
+        {{ build_meta.tag }}@{{ build_meta.commit }} | render time: {{ rt.total }}s
         <div id="perf-details" class="perf-breakdown">
             {{ rt.breakdown }}
         </div>

templates/fees-juniors.html

@@ -238,7 +238,7 @@
     {% set rt = get_render_time() %}
     <div class="footer"
         onclick="document.getElementById('perf-details').style.display = (document.getElementById('perf-details').style.display === 'block' ? 'none' : 'block')">
-        render time: {{ rt.total }}s
+        {{ build_meta.tag }}@{{ build_meta.commit }} | render time: {{ rt.total }}s
         <div id="perf-details" class="perf-breakdown">
             {{ rt.breakdown }}
         </div>

templates/fees.html

@@ -253,7 +253,7 @@
     {% set rt = get_render_time() %}
     <div class="footer"
         onclick="document.getElementById('perf-details').style.display = (document.getElementById('perf-details').style.display === 'block' ? 'none' : 'block')">
-        render time: {{ rt.total }}s
+        {{ build_meta.tag }}@{{ build_meta.commit }} | render time: {{ rt.total }}s
         <div id="perf-details" class="perf-breakdown">
             {{ rt.breakdown }}
         </div>

templates/juniors.html

@@ -628,7 +628,7 @@
     {% set rt = get_render_time() %}
     <div class="footer"
         onclick="document.getElementById('perf-details').style.display = (document.getElementById('perf-details').style.display === 'block' ? 'none' : 'block')">
-        render time: {{ rt.total }}s
+        {{ build_meta.tag }}@{{ build_meta.commit }} | render time: {{ rt.total }}s
         <div id="perf-details" class="perf-breakdown">
             {{ rt.breakdown }}
         </div>

templates/payments.html

@@ -237,7 +237,7 @@
     {% set rt = get_render_time() %}
     <div class="footer"
         onclick="document.getElementById('perf-details').style.display = (document.getElementById('perf-details').style.display === 'block' ? 'none' : 'block')">
-        render time: {{ rt.total }}s
+        {{ build_meta.tag }}@{{ build_meta.commit }} | render time: {{ rt.total }}s
         <div id="perf-details" class="perf-breakdown">
             {{ rt.breakdown }}
         </div>

templates/reconcile-juniors.html

@@ -631,7 +631,7 @@
     {% set rt = get_render_time() %}
     <div class="footer"
         onclick="document.getElementById('perf-details').style.display = (document.getElementById('perf-details').style.display === 'block' ? 'none' : 'block')">
-        render time: {{ rt.total }}s
+        {{ build_meta.tag }}@{{ build_meta.commit }} | render time: {{ rt.total }}s
         <div id="perf-details" class="perf-breakdown">
             {{ rt.breakdown }}
         </div>

templates/reconcile.html

@@ -631,7 +631,7 @@
     {% set rt = get_render_time() %}
     <div class="footer"
         onclick="document.getElementById('perf-details').style.display = (document.getElementById('perf-details').style.display === 'block' ? 'none' : 'block')">
-        render time: {{ rt.total }}s
+        {{ build_meta.tag }}@{{ build_meta.commit }} | render time: {{ rt.total }}s
         <div id="perf-details" class="perf-breakdown">
             {{ rt.breakdown }}
         </div>