Fix version output when no version is injected (i.e: go install)

doc.go

@@ -0,0 +1,2 @@
+// Package saltyim is a secure, easy, self-hosted messaging
+package saltyim

version.go

@@ -6,28 +6,41 @@ import (
 	"strings"
 )
 
+const (
+	defaultVersion = "0.0.0"
+	defaultCommit  = "HEAD"
+	defaultBuild   = "0000-01-01:00:00+00:00"
+)
+
 var (
 	// Version is the tagged release version in the form <major>.<minor>.<patch>
 	// following semantic versioning and is overwritten by the build system.
-	Version = "0.0.0"
+	Version = defaultVersion
 
 	// Commit is the commit sha of the build (normally from Git) and is overwritten
 	// by the build system.
-	Commit = "HEAD"
+	Commit = defaultCommit
 
 	// Build is the date and time of the build as an RFC3339 formatted string
 	// and is overwritten by the build system.
-	Build = "0000-01-01:00:00+00:00"
+	Build = defaultBuild
 )
 
 // FullVersion display the full version and build
 func FullVersion() string {
 	var sb strings.Builder
 
-	sb.WriteString(fmt.Sprintf("%s@%s %s", Version, Commit, Build))
+	isDefault := Version == defaultVersion && Commit == defaultCommit && Build == defaultBuild
+
+	if !isDefault {
+		sb.WriteString(fmt.Sprintf("%s@%s %s", Version, Commit, Build))
+	}
 
 	if info, ok := debug.ReadBuildInfo(); ok {
-		sb.WriteString(fmt.Sprintf(" %s %s", info.Main.Version, info.GoVersion))
+		if isDefault {
+			sb.WriteString(fmt.Sprintf(" %s", info.Main.Version))
+		}
+		sb.WriteString(fmt.Sprintf(" %s", info.GoVersion))
 		if info.Main.Sum != "" {
 			sb.WriteString(fmt.Sprintf(" %s", info.Main.Sum))
 		}