Render version of perfdash on UI

perfdash/Makefile

@@ -1,13 +1,22 @@
 all: push
 
 # See deployment.yaml for the version currently running-- bump this ahead before rebuilding!
+# Additionally please ensure to update the same in www/VERSION
 TAG?=2.56
+WWW_VERSION=$(shell cat www/VERSION)
 
 REPO?=gcr.io/k8s-staging-perf-tests
 
 .PHONY: test
+test: WWW_VERSION = $(shell cat www/VERSION)
+
 test: perfdash.go parser.go config.go metrics-downloader-helper.go metrics-downloader.go gcs_metrics_bucket.go s3_metrics_bucket.go local_metrics_dir.go
 	go test
+	@WWW_VERSION=$$(cat www/VERSION); \
+	if [ "$(TAG)" != "$$WWW_VERSION" ]; then \
+		echo "Version mismatch! Makefile=$(TAG), www/VERSION=$(WWW_VERSION). Please align" >&2; \
+		exit 1; \
+	fi
 
 perfdash: test
 	go build -a -installsuffix cgo -ldflags '-w' -o perfdash

perfdash/www/VERSION

@@ -0,0 +1 @@
+2.56

perfdash/www/index.html

@@ -54,9 +54,15 @@ <h1 class="md-display-2">Performance Dashboard</h1>
         </canvas>
         <p style="text-align: center">Runs over time</p>
       </div>
-      <p style="font-size: x-small; font-style: italic">
-        Click a data point to see build logs. CTRL+click anywhere to trim outliers.
+      <p style="font-size: x-small; font-style: italic; display: flex; justify-content: space-between;">
+        <span>Click a data point to see build logs. CTRL+click anywhere to trim outliers.</span>
+        <span>Version: <span id="version"></span></span>
       </p>
+      <script>
+        fetch('VERSION')
+                .then(resp => resp.text())
+                .then(version => document.getElementById('version').innerText = version)
+      </script>
       <!-- Angular Material Dependencies -->
       <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.3.15/angular.min.js"></script>
       <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.3.15/angular-animate.min.js"></script>