feat: add GitHub repository dashboard with Prometheus metrics

ghtracker authenticates as a GitHub App and scans a configured list of repositories on a schedule. It serves a dashboard, a JSON state endpoint, a health probe and Prometheus metrics.

The dashboard lists only items that need attention: failing workflows, pull requests that wait too long or fail their checks, stale issues and projects that failed to scan. It has search, dynamic filters and a button that rescans on demand. The Vue app is embedded in the Go binary.

The client protects the GitHub rate limit with conditional requests, a request reserve and Retry-After handling.

main_test.go

@@ -0,0 +1,133 @@
+package main
+
+import (
+	"context"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/pem"
+	"fmt"
+	"io"
+	"log/slog"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func freeAddr(t *testing.T) string {
+	t.Helper()
+	l, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer l.Close()
+	return l.Addr().String()
+}
+
+func get(t *testing.T, url string) (int, string) {
+	t.Helper()
+	req, err := http.NewRequestWithContext(context.Background(), http.MethodGet, url, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return 0, ""
+	}
+	defer func() { _ = resp.Body.Close() }()
+	b, _ := io.ReadAll(resp.Body)
+	return resp.StatusCode, string(b)
+}
+
+// TestEndToEnd wires config, app auth, collector, metrics and web against a fake GitHub API.
+func TestEndToEnd(t *testing.T) {
+	var apiCalls atomic.Int64
+	gh := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		apiCalls.Add(1)
+		p := r.URL.Path
+		switch {
+		case strings.HasSuffix(p, "/installation"):
+			fmt.Fprint(w, `{"id":1}`)
+		case strings.HasPrefix(p, "/app/installations/"):
+			fmt.Fprintf(w, `{"token":"t","expires_at":%q}`, time.Now().Add(time.Hour).UTC().Format(time.RFC3339))
+		case p == "/repos/o/r":
+			fmt.Fprint(w, `{"html_url":"https://github.com/o/r","default_branch":"main"}`)
+		case p == "/repos/o/r/issues", p == "/repos/o/r/pulls", p == "/repos/o/r/tags":
+			fmt.Fprint(w, `[]`)
+		case p == "/repos/o/r/actions/workflows":
+			fmt.Fprint(w, `{"workflows":[{"id":1,"name":"CI","html_url":"w","state":"active"}]}`)
+		case p == "/repos/o/r/actions/workflows/1/runs":
+			fmt.Fprint(w, `{"workflow_runs":[{"id":1,"html_url":"r","event":"push","head_branch":"main","status":"completed","conclusion":"failure","created_at":"2026-10-01T00:00:00Z"}]}`)
+		case p == "/repos/o/r/releases/latest":
+			fmt.Fprint(w, `{"tag_name":"v9.9.9","html_url":"rel","published_at":"2026-10-01T00:00:00Z"}`)
+		default:
+			http.NotFound(w, r)
+		}
+	}))
+	defer gh.Close()
+
+	key, _ := rsa.GenerateKey(rand.Reader, 2048)
+	dir := t.TempDir()
+	keyPath := filepath.Join(dir, "k.pem")
+	_ = os.WriteFile(keyPath, pem.EncodeToMemory(&pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(key)}), 0o600)
+	addr := freeAddr(t)
+	cfgPath := filepath.Join(dir, "c.yaml")
+	cfg := fmt.Sprintf("listen: %q\ngithub:\n  app_id: 1\n  private_key_file: %s\n  api_url: %s\nrepos: [o/r]\n", addr, keyPath, gh.URL)
+	_ = os.WriteFile(cfgPath, []byte(cfg), 0o600)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	done := make(chan error, 1)
+	go func() { done <- run(ctx, cfgPath, slog.New(slog.NewTextHandler(io.Discard, nil))) }()
+
+	base := "http://" + addr
+	deadline := time.Now().Add(10 * time.Second)
+	for {
+		if code, _ := get(t, base+"/healthz"); code == 200 {
+			break
+		}
+		if time.Now().After(deadline) {
+			t.Fatal("server never became healthy")
+		}
+		time.Sleep(20 * time.Millisecond)
+	}
+
+	_, metrics := get(t, base+"/metrics")
+	for _, want := range []string{
+		`ghtracker_repo_up{repo="o/r"} 1`,
+		`ghtracker_workflow_failing{background="false",repo="o/r",workflow="CI"} 1`,
+		`ghtracker_release_info{repo="o/r",url="rel",version="v9.9.9"} 1`,
+		`ghtracker_repo_health{repo="o/r"} 2`,
+		`ghtracker_alerts{severity="crit"} 1`,
+		"ghtracker_refreshes_total 1",
+	} {
+		if !strings.Contains(metrics, want) {
+			t.Errorf("metrics missing %q", want)
+		}
+	}
+	_, state := get(t, base+"/api/state")
+	for _, want := range []string{`"tag":"v9.9.9"`, `"failure on main (push)"`, `"health":"crit"`} {
+		if !strings.Contains(state, want) {
+			t.Errorf("state missing %q", want)
+		}
+	}
+
+	if n := apiCalls.Load(); n > 12 {
+		t.Errorf("one refresh of one repo used %d API calls, want a handful", n)
+	}
+
+	cancel()
+	select {
+	case err := <-done:
+		if err != nil {
+			t.Fatalf("shutdown: %v", err)
+		}
+	case <-time.After(5 * time.Second):
+		t.Fatal("no graceful shutdown")
+	}
+}