build: Handle test folders as task inputs

The test folders are not jar task inputs. But they are test task inputs
except for content created by the test execution. We exclude that by
excluding empty folders and git ignored content.

Signed-off-by: BJ Hargrave <bj@bjhargrave.com>

build.gradle

@@ -36,13 +36,29 @@ subprojects {
     if (JavaVersion.current().isJava8Compatible()) {
       javadoc.options.addStringOption('Xdoclint:none', '-quiet') 
     }
+    /* test folders are not part of jar but used by unit tests  */
+    def testfolders = ['testresources/', 'testdata/']
+    jar {
+      projectDirInputsExcludes << '.*'
+      projectDirInputsExcludes += testfolders
+    }
     test {
       testLogging {
         exceptionFormat 'full'
       }
       inputs.files fileTree(projectDir) {
-        include 'testresources/**'
-        include 'testdata/**'
+        include testfolders
+        exclude {
+          def f = it.file
+          if (f.directory && f.list().length == 0) {
+            return true
+          }
+          try {
+            return "git check-ignore ${f}".execute().waitFor() == 0
+          } catch (Exception e) {
+            return false
+          }
+        }
       }
     }
   }