feat: Add version command

When building with Go 1.18+ (we're on 1.22 now), we get version control
info in the binary! Since we don't set version numbers, the commit hash
(revision) is all we have to identify the version of the code that's
running.

This adds a `version` chat command that returns a formatted "current
build" string. It looks something like this:

    github.com/recursecenter/pairing-bot (1234567890abcdef1234567890abcdef12345678, built with go1.23.0)

And since it might be useful to us for debugging, this also prints the
whole buildinfo string at startup.

dispatch.go

@@ -226,6 +226,8 @@ func dispatch(ctx context.Context, pl *PairingLogic, cmd string, cmdArgs []strin
 		response = getCookieClubMessage()
 	case "help":
 		response = helpMessage
+	case "version":
+		response = pl.version
 	default:
 		// this won't execute because all input has been sanitized
 		// by parseCmd() and all cases are handled explicitly above

dispatch_test.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"context"
+	"testing"
+)
+
+func Test_dispatch(t *testing.T) {
+	ctx := context.Background()
+	projectID := fakeProjectID(t)
+
+	client := testFirestoreClient(t, ctx, projectID)
+
+	pl := &PairingLogic{
+		rdb:     &FirestoreRecurserDB{client},
+		version: "test string",
+	}
+
+	t.Run("version", func(t *testing.T) {
+		resp, err := dispatch(ctx, pl, "version", nil, 0, "[email protected]", "Your Name")
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		expected := "test string"
+		if resp != expected {
+			t.Errorf("expected %q, got %q", expected, resp)
+		}
+	})
+}

main.go

@@ -7,6 +7,7 @@ import (
 	"log"
 	"net/http"
 	"os"
+	"runtime/debug"
 
 	"cloud.google.com/go/firestore"
 	"github.com/recursecenter/pairing-bot/zulip"
@@ -19,6 +20,16 @@ func main() {
 	// and the file:line (without the full path- we don't have directories.)
 	log.SetFlags(log.Ldate | log.Ltime | log.LUTC | log.Lshortfile)
 
+	// Pre-format the version string from built-in debug info.
+	var version string
+	if bi, ok := debug.ReadBuildInfo(); ok {
+		log.Print(bi)
+		version = formatVersion(bi)
+	} else {
+		log.Print("Warning: no build info in binary")
+		version = "(unknown)"
+	}
+
 	ctx := context.Background()
 
 	appEnv := os.Getenv("APP_ENV")
@@ -98,7 +109,8 @@ func main() {
 		rcapi: rcapi,
 		revdb: revdb,
 
-		zulip: zulipClient,
+		zulip:   zulipClient,
+		version: version,
 	}
 
 	http.HandleFunc("/", http.NotFound)           // will this handle anything that's not defined?
@@ -123,3 +135,24 @@ func main() {
 	log.Printf("Listening on port %s", port)
 	log.Fatal(http.ListenAndServe(fmt.Sprintf(":%s", port), nil))
 }
+
+func formatVersion(bi *debug.BuildInfo) string {
+	goModule := bi.Path
+	goVersion := bi.GoVersion
+
+	var revision string
+	var modified string
+
+	for _, setting := range bi.Settings {
+		switch setting.Key {
+		case "vcs.revision":
+			revision = setting.Value
+		case "vcs.modified":
+			if setting.Value == "true" {
+				modified = "+"
+			}
+		}
+	}
+
+	return fmt.Sprintf("%s (%s%s, built with %s)", goModule, revision, modified, goVersion)
+}

pairing_bot.go

@@ -30,7 +30,8 @@ type PairingLogic struct {
 	revdb ReviewDB
 	rcapi RecurseAPI
 
-	zulip *zulip.Client
+	zulip   *zulip.Client
+	version string
 }
 
 func (pl *PairingLogic) handle(w http.ResponseWriter, r *http.Request) {

parse_cmd.go

@@ -30,6 +30,7 @@ func parseCmd(cmdStr string) (string, []string, error) {
 		"add-review",
 		"get-reviews",
 		"cookie",
+		"version",
 	}
 
 	//This contains the days of the week and common abbreviations
@@ -116,6 +117,8 @@ func parseCmd(cmdStr string) (string, []string, error) {
 			}
 
 			return "schedule", userSchedule, err
+		case cmd[0] == "version":
+			return "version", nil, nil
 		default:
 			return cmd[0], cmd[1:], err
 		}

parse_cmd_test.go

@@ -31,6 +31,7 @@ var tableNoArgs = []struct {
 	{"help_wrong_usage", "help me", "help", nil, true},
 	{"status_correct_usage", "status", "status", nil, false},
 	{"status_wrong_usage", "status me", "help", nil, true},
+	{"version", "version", "version", nil, false},
 }
 
 func TestParseCmdNoArgs(t *testing.T) {
@@ -73,6 +74,7 @@ var tableWithArgs = []struct {
 	{"unskip_wrong_usage", "unskip today", "help", nil, true},
 	{"unskip_wrong_usage", "unskip friday", "help", nil, true},
 	{"unskip_wrong_usage", "unskip", "help", nil, true},
+	{"version_extra_args_ok", "version info", "version", nil, false},
 }
 
 func TestParseCmdWithArgs(t *testing.T) {
@@ -98,6 +100,8 @@ func TestParseCmdWithArgs(t *testing.T) {
 				if gotArgs[0] != "tomorrow" {
 					t.Errorf("Wrong argument %v for command %v\n", gotArgs[0], gotCmd)
 				}
+			case "version":
+				// Always fine as long as the wantedCmd check passes.
 			default:
 				if gotCmd != "help" {
 					t.Errorf("unknown command %v\n", gotCmd)