Refactor tag logic to its own helper

vars/checkoutStep.groovy

@@ -1,16 +1,5 @@
 #!/usr/bin/env groovy
 
-String call(Map config = [:]) {
-    Map defaults = [
-        dirtyFlag: '-dirty'
-    ]
-    Map runConfig = defaults + config
-
+void call() {
     checkout scm
-
-    gitTag = sh(
-        script: "git describe --tags --always --dirty=${runConfig.dirtyFlag}",
-        returnStdout: true
-      ).trim()
-    return gitTag
 }

vars/getCurrentTag.groovy

@@ -0,0 +1,14 @@
+#!/usr/bin/env groovy
+
+String call(Map config = [:]) {
+    Map defaults = [
+        dirtyFlag: '-dirty'
+    ]
+    Map runConfig = defaults + config
+
+    gitTag = sh(
+        script: "git describe --tags --always --dirty=${runConfig.dirtyFlag}",
+        returnStdout: true
+      ).trim()
+    return gitTag
+}