Add a version command (#159)

Makefile

@@ -5,12 +5,14 @@ PREFIX=/usr/local
 BINDIR=$(PREFIX)/bin
 MANDIR=$(PREFIX)/share/man
 GO=go
+TAGGED_RELEASE!=git describe --tags --abbrev=0
+LDFLAGS=-X "github.com/bouncepaw/mycorrhiza/version.taggedRelease=$(TAGGED_RELEASE)"
 
 all: mycorrhiza
 
 mycorrhiza:
 	$(GO) generate $(GOFLAGS)
-	CGO_ENABLED=0 $(GO) build $(GOFLAGS) -o mycorrhiza .
+	CGO_ENABLED=0 $(GO) build -ldflags="$(LDFLAGS)" $(GOFLAGS) -o mycorrhiza .
 
 install:
 	mkdir -m755 -p $(DESTDIR)$(BINDIR) $(DESTDIR)$(MANDIR)/man1

flag.go

@@ -13,6 +13,7 @@ import (
 	"github.com/bouncepaw/mycorrhiza/cfg"
 	"github.com/bouncepaw/mycorrhiza/files"
 	"github.com/bouncepaw/mycorrhiza/user"
+	"github.com/bouncepaw/mycorrhiza/version"
 	"golang.org/x/term"
 )
 
@@ -31,12 +32,19 @@ func printHelp() {
 // parseCliArgs parses CLI options and sets several important global variables. Call it early.
 func parseCliArgs() {
 	var createAdminName string
+	var versionFlag bool
 
 	flag.StringVar(&cfg.ListenAddr, "listen-addr", "", "Address to listen on. For example, 127.0.0.1:1737 or /run/mycorrhiza.sock.")
 	flag.StringVar(&createAdminName, "create-admin", "", "Create a new admin. The password will be prompted in the terminal.")
+	flag.BoolVar(&versionFlag, "version", false, "Print version information and exit.")
 	flag.Usage = printHelp
 	flag.Parse()
 
+	if versionFlag {
+		fmt.Println(version.FormatVersion())
+		os.Exit(0)
+	}
+
 	args := flag.Args()
 	if len(args) == 0 {
 		log.Fatal("error: pass a wiki directory")

version/version.go

@@ -0,0 +1,32 @@
+package version
+
+import (
+	"fmt"
+	"runtime/debug"
+	"strconv"
+)
+
+// This is set through ldflags='-X ...' in the Makefile
+var taggedRelease string = "Unknown"
+
+func FormatVersion() string {
+	var commitHash string = "Unknown"
+	var dirty string = ""
+
+	info, ok := debug.ReadBuildInfo()
+
+	if ok {
+		for _, setting := range info.Settings {
+			if setting.Key == "vcs.revision" {
+				commitHash = setting.Value
+			} else if setting.Key == "vcs.modified" {
+				modified, err := strconv.ParseBool(setting.Value)
+				if err == nil && modified {
+					dirty = "-dirty"
+				}
+			}
+		}
+	}
+
+	return fmt.Sprintf("Mycorrhiza Wiki %s+%s%s", taggedRelease, commitHash[:7], dirty)
+}