/TagStrategy: fail the build with meaningful error message when 'v' is used as a tag

Author: rpalcolea

src/integTest/groovy/nebula/plugin/release/ReleasePluginIntegrationSpec.groovy

@@ -682,6 +682,18 @@ class ReleasePluginIntegrationSpec extends GitVersioningIntegrationSpec {
         !new File(projectDir, "build/libs/${moduleName}-3.1.2-rc.1.jar").exists()
     }
 
+    def 'using v as tag fails when running tasks'() {
+        git.tag.add(name: "v3.1.2")
+        git.tag.add(name: "v")
+
+        when:
+        def result = runTasksWithFailure('final', '-Prelease.useLastTag=true')
+
+        then:
+        result.standardError.contains "Tag name 'v' is invalid. 'v' should be use as prefix for semver versions only, example: v1.0.0"
+        !new File(projectDir, "build/libs/${moduleName}-3.1.2.jar").exists()
+    }
+
     def 'useLastTag uses release tag when running "final"'() {
         git.tag.add(name: "v3.1.2-rc.1")
         git.tag.add(name: "v3.1.2")

src/main/groovy/nebula/plugin/release/git/base/TagStrategy.groovy

@@ -20,6 +20,7 @@ import com.github.zafarkhaja.semver.Version
 import groovy.transform.CompileDynamic
 import org.ajoberstar.grgit.Grgit
 import org.ajoberstar.grgit.Tag
+import org.gradle.api.GradleException
 import org.slf4j.Logger
 import org.slf4j.LoggerFactory
 
@@ -40,6 +41,9 @@ class TagStrategy {
      */
     Closure<Version> parseTag = { Tag tag ->
         try {
+            if(tag.name == 'v') {
+                throw new GradleException("Tag name '${tag.name}' is invalid. 'v' should be use as prefix for semver versions only, example: v1.0.0")
+            }
             Version.valueOf(tag.name[0] == 'v' ? tag.name[1..-1] : tag.name)
         } catch (ParseException e) {
             null