Explicit release prop check in rebuild strategy

Rebuild strategy used to look for any property on the project that
started with release. This could cause some issues with model rules and
projects with evaluationDependsOnChildren. Explicitly looking for the
properties avoids this issue.

Fixes #252

src/main/groovy/org/ajoberstar/gradle/git/release/semver/RebuildVersionStrategy.groovy

@@ -53,14 +53,14 @@ class RebuildVersionStrategy implements VersionStrategy {
     @Override
     boolean selector(Project project, Grgit grgit) {
         def clean = grgit.status().clean
-        def props = project.properties.keySet().find { it.startsWith('release.') }
+        def propsSpecified = project.hasProperty(SemVerStrategy.SCOPE_PROP) || project.hasProperty(SemVerStrategy.STAGE_PROP)
         def headVersion = getHeadVersion(project, grgit)
 
-        if (clean && props == null && headVersion) {
+        if (clean && !propsSpecified && headVersion) {
             logger.info('Using {} strategy because repo is clean, no "release." properties found and head version is {}', name, headVersion)
             return true
         } else {
-            logger.info('Skipping {} strategy because clean is {}, "release." properties are {} and head version is {}', name, clean, props, headVersion)
+            logger.info('Skipping {} strategy because clean is {}, "release." properties are {} and head version is {}', name, clean, propsSpecified, headVersion)
             return false
         }
     }

src/test/groovy/org/ajoberstar/gradle/git/release/semver/RebuildVersionStrategySpec.groovy

@@ -51,7 +51,7 @@ class RebuildVersionStrategySpec extends Specification {
     def 'selector returns false if any release properties are set'() {
         given:
         mockClean(true)
-        Project project = getProject('release.anything': 'value')
+        Project project = getProject('release.scope': 'value')
         mockTagsAtHead('v1.0.0')
         expect:
         !strategy.selector(project, grgit)