improved buildvars defaults

Author: Jannes-Dailidow

.vscode/launch.json

@@ -23,7 +23,7 @@
             "console": "integratedTerminal",
             "hideSystemGoroutines": true,
             "buildFlags": [
-                "-ldflags=-X github.com/toeirei/keymaster/buildvars.Version=development"
+                "-ldflags=-X github.com/toeirei/keymaster/buildvars.Version=dev"
             ]
         },
         {

buildvars/vars.go

@@ -5,5 +5,41 @@
 // Package buildvars contains variables injected at build time.
 package buildvars
 
+import (
+	"runtime/debug"
+)
+
 // Version is set at link time via `-ldflags -X github.com/toeirei/keymaster/buildvars.Version=...`.
-var Version string = "unknown version"
+var Version string
+
+func init() {
+	if Version == "" {
+		Version = "unknown"
+
+		if buildInfo, ok := debug.ReadBuildInfo(); ok {
+			var vcs, vcsRevision, vcsModified string
+			for _, setting := range buildInfo.Settings {
+				switch setting.Key {
+				case "vcs":
+					vcs = setting.Value
+				case "vcs.revision":
+					vcsRevision = setting.Value
+				case "vcs.modified":
+					vcsModified = setting.Value
+				}
+			}
+
+			if vcs != "" && vcsRevision != "" {
+				if vcs == "git" {
+					vcsRevision = vcsRevision[:7]
+				}
+
+				Version = vcs + ":" + vcsRevision
+
+				if vcsModified == "true" {
+					Version += "*"
+				}
+			}
+		}
+	}
+}