Add self-update, including in Docker

Sandbar can install new releases itself using Reef's selfupdate, automatically with
SANDBAR_AUTO_UPDATE=1 or from a button on the Account page. In a container the new binary is
written to <data>/bin and takes over from the image at start, until the image catches up.
Tags now publish a Gitea release with archives and SHA256SUMS as well as the image.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

internal/sandbar/update_test.go

@@ -0,0 +1,109 @@
+package sandbar
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+func TestVersionNewer(t *testing.T) {
+	for _, c := range []struct {
+		a, b string
+		want bool
+	}{
+		{"v0.1.4", "v0.1.3", true},
+		{"v0.2.0", "v0.1.9", true},
+		{"v1.0.0", "v0.9.9", true},
+		{"v0.1.3", "v0.1.3", false},
+		{"v0.1.2", "v0.1.3", false},
+		{"v0.1.10", "v0.1.9", true},
+		{"v0.2.0-rc1", "v0.1.0", false}, // pre-releases are never offered
+		{"v0.2.0", "dev", false},        // a development build never updates
+		{"dev", "v0.1.0", false},
+	} {
+		if got := versionNewer(c.a, c.b); got != c.want {
+			t.Errorf("versionNewer(%q, %q) = %v, want %v", c.a, c.b, got, c.want)
+		}
+	}
+}
+
+// The update page asks the release server and reports whether it has something newer.
+func TestUpdateStatus(t *testing.T) {
+	release := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/api/v1/repos/Veillax/sandbar/releases/latest" {
+			http.NotFound(w, r)
+			return
+		}
+		w.Write([]byte(`{"tag_name":"v0.2.0","assets":[]}`))
+	}))
+	defer release.Close()
+
+	s, _, _ := newTestServer(t)
+	s.opts.Version, s.opts.UpdateServer = "v0.1.0", release.URL
+	ts := httptest.NewServer(s.Handler())
+	defer ts.Close()
+	c := newAPIClient(t, ts)
+
+	if code := c.do("GET", "/api/v1/system/update", nil, nil); code != 401 {
+		t.Fatalf("signed out: %d", code)
+	}
+	c.setup()
+	var st map[string]any
+	if code := c.do("GET", "/api/v1/system/update", nil, &st); code != 200 {
+		t.Fatalf("status: %d", code)
+	}
+	if st["current"] != "v0.1.0" || st["latest"] != "v0.2.0" || st["newer"] != true {
+		t.Fatalf("status: %v", st)
+	}
+	if st["error"] != "" {
+		t.Fatalf("unexpected error: %v", st["error"])
+	}
+
+	// A development build can look but not install.
+	s.opts.Version = "dev"
+	s.upd.checked = s.upd.checked.AddDate(-1, 0, 0)
+	if code := c.do("POST", "/api/v1/system/update", map[string]string{}, &st); code != 400 {
+		t.Fatalf("a development build must not install: %d %v", code, st)
+	}
+}
+
+// A newer binary on the data volume takes over from the image, and a stale one is removed.
+func TestOverlay(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("self-update is not supported on Windows")
+	}
+	dir := t.TempDir()
+	bin := filepath.Join(dir, "bin")
+	os.MkdirAll(bin, 0o755)
+	overlay := filepath.Join(bin, "sandbar")
+	script := func(version string) {
+		os.WriteFile(overlay, []byte("#!/bin/sh\necho 'sandbar "+version+"'\n"), 0o755)
+	}
+	var logged []string
+	logf := func(f string, a ...any) { logged = append(logged, f) }
+
+	// An older overlay is deleted once the image is a release that has caught up.
+	script("v0.1.0")
+	UseNewerOverlay(dir, "v0.1.5", logf)
+	if _, err := os.Stat(overlay); err == nil {
+		t.Fatal("a stale overlay should be removed")
+	}
+
+	// A development image never deletes or switches to anything.
+	script("v0.9.0")
+	UseNewerOverlay(dir, "dev", logf)
+	if _, err := os.Stat(overlay); err != nil {
+		t.Fatal("a development build must leave the overlay alone")
+	}
+
+	// Something that does not report a version is ignored, not run.
+	os.WriteFile(overlay, []byte("#!/bin/sh\necho hello\n"), 0o755)
+	UseNewerOverlay(dir, "v0.1.5", logf)
+	if len(logged) == 0 || !strings.Contains(logged[len(logged)-1], "did not report a version") {
+		t.Fatalf("log: %v", logged)
+	}
+}