fix f-droid build

.travis.yml

@@ -9,7 +9,9 @@ android:
     # Additional components
     - extra-google-m2repository
     - extra-android-m2repository
-script: ./gradlew assembleDebug lintDebug testDebug checkDebugDuplicateClasses checkDebugManifest
+script:
+  - ./gradlew assembleDebug lintDebug testDebug checkDebugDuplicateClasses checkDebugManifest
+  - ./gradlew checkUpdatedLicenseFile
 before_cache:
   - rm -f  $HOME/.gradle/caches/modules-2/modules-2.lock
   - rm -fr $HOME/.gradle/caches/*/plugin-resolution/

app/.gitignore

@@ -1,2 +1 @@
 /build
-/src/main/assets/open_source_licenses.html

app/build.gradle

@@ -52,7 +52,7 @@ android {
         applicationId getBuildApplicationId()
         minSdkVersion 14
         targetSdkVersion 28
-        versionCode 18
+        versionCode 19
         versionName scmVersion.version
     }
     signingConfigs {
@@ -77,23 +77,9 @@ android {
 }
 
 afterEvaluate {
-    preBuild.dependsOn(generateLicenseFile)
     preBuild.dependsOn(checkVersionCode)
 }
 
-// work around empty license file bug
-// see https://github.com/jaredsburrows/gradle-license-plugin/issues/38
-task generateLicenseFile(type: Exec) {
-    inputs.file(buildFile)
-    outputs.file("${project.projectDir}/src/main/assets/open_source_licenses.html")
-    workingDir project.rootDir
-    if (Os.isFamily(Os.FAMILY_WINDOWS)) {
-        commandLine 'gradlew.bat', 'app:licenseReleaseReport'
-    } else {
-        commandLine './gradlew', 'app:licenseReleaseReport'
-    }
-}
-
 task checkVersionCode {
     doLast {
         if (android.defaultConfig.versionCode != getBuildVersionCode()) {
@@ -102,6 +88,17 @@ task checkVersionCode {
     }
 }
 
+afterEvaluate {
+    task checkUpdatedLicenseFile {
+        dependsOn licenseDebugReport
+        doLast {
+            if (grgit.status().unstaged.modified.contains('app/src/main/assets/open_source_licenses.html')) {
+                throw new InvalidUserDataException('License file has changed, please commit new version first')
+            }
+        }
+    }
+}
+
 play {
     serviceAccountCredentials = file("../../google-key.json")
 }