Fix tagPrefix/vTagPrefix coherence

project/plugins.sbt

@@ -1,3 +1,3 @@
-addSbtPlugin("com.dwijnand"      % "sbt-dynver"      % "4.0.0")
+addSbtPlugin("com.dwijnand"      % "sbt-dynver"      % "4.1.0")
 addSbtPlugin("com.typesafe"      % "sbt-mima-plugin" % "0.7.0")
 addSbtPlugin("org.foundweekends" % "sbt-bintray"     % "0.5.6")

src/main/scala/sbtdynver/DynVerPlugin.scala

@@ -55,8 +55,8 @@ object DynVerPlugin extends AutoPlugin {
     previousStableVersion   := dynverGitPreviousStableVersion.value.previousVersion,
 
     dynverInstance := {
-      val tagPrefix = dynverTagPrefix.value
       val vTagPrefix = dynverVTagPrefix.value
+      val tagPrefix = dynverTagPrefix.?.value.getOrElse(if (vTagPrefix) "v" else "")
       assert(vTagPrefix ^ tagPrefix != "v", s"Incoherence: dynverTagPrefix=$tagPrefix vs dynverVTagPrefix=$vTagPrefix")
       DynVer(Some(buildBase.value), dynverSeparator.value, tagPrefix)
     },
@@ -66,8 +66,7 @@ object DynVerPlugin extends AutoPlugin {
     dynverSonatypeSnapshots        := false,
     dynverGitPreviousStableVersion := dynverInstance.value.getGitPreviousStableTag,
     dynverSeparator                := DynVer.separator,
-    dynverTagPrefix                := DynVer.tagPrefix,
-    dynverVTagPrefix               := dynverTagPrefix.value == "v",
+    dynverVTagPrefix               := dynverTagPrefix.??(DynVer.tagPrefix).value == "v",
 
     dynver                  := {
       val dynver = dynverInstance.value

src/sbt-test/dynver/no-v-tag-prefix/build.sbt

@@ -0,0 +1 @@
+dynverVTagPrefix in ThisBuild := false

src/sbt-test/dynver/no-v-tag-prefix/project/plugins.sbt

@@ -0,0 +1,5 @@
+sys.props.get("plugin.version") match {
+  case Some(x) => addSbtPlugin("com.dwijnand" % "sbt-dynver" % x)
+  case _       => sys.error("""|The system property 'plugin.version' is not defined.
+                               |Specify this property using the scriptedLaunchOpts -D.""".stripMargin)
+}

src/sbt-test/dynver/no-v-tag-prefix/test

@@ -0,0 +1 @@
+> about