feature add detektAnalysis task

gradle/plugins/src/main/java/static_analysis/linters/DetektLinter.kt

@@ -15,6 +15,7 @@ import java.io.File
 class DetektLinter : Linter {
 
     private companion object {
+        const val TAG = "DetektLinter"
         const val ONLY_DIFFS_FLAG = "only-diffs"
         const val GET_GIT_DIFFS_COMMAND = "git diff --name-only --ignore-submodules"
     }
@@ -58,20 +59,30 @@ class DetektLinter : Linter {
                     }
                 }
 
-                val isOnlyDiffs = properties["args"] == ONLY_DIFFS_FLAG // example: ./gradlew detektAnalysis -Pargs="only-diffs"
-
-                source = getSources(extension.excludes, isOnlyDiffs, project)
+                val diffsBranch = properties[ONLY_DIFFS_FLAG] as? String
+                source = getSources(extension.excludes, diffsBranch, project)
             }
         }
     }
 
-    private fun getSources(excludes: String, isOnlyDiffs: Boolean, project: Project): FileTree = when {
-        isOnlyDiffs -> getGitDiffFiles(excludes, project)
-        else -> project.getSources(excludes)
+    private fun getSources(excludes: String, diffsBranch: String?, project: Project): FileTree = when (diffsBranch) {
+        null -> project.getSources(excludes)
+        else -> getGitDiffFiles(excludes, diffsBranch, project)
     }
 
-    private fun getGitDiffFiles(excludes: String, project: Project): FileTree {
-        val gitDiffs = GET_GIT_DIFFS_COMMAND.runCommand() ?: return project.files().asFileTree
+    private fun getGitDiffFiles(excludes: String, diffsBranch: String, project: Project): FileTree {
+        val getGitDiffsCommand = if (diffsBranch.isEmpty()) {
+            GET_GIT_DIFFS_COMMAND
+        } else {
+            GET_GIT_DIFFS_COMMAND.plus(" --merge-base $diffsBranch")
+        }
+
+        val gitDiffs = getGitDiffsCommand.runCommand()
+
+        if (gitDiffs.isNullOrEmpty()) {
+            project.logger.error("$TAG: Diffs are empty or specified branch or commit does not exists")
+            return project.files().asFileTree
+        }
 
         val diffFiles = gitDiffs.lines()
                 .map { File(it) }

gradle/plugins/src/main/java/static_analysis/plugins/StaticAnalysisAndroidPlugin.kt

@@ -27,7 +27,14 @@ class StaticAnalysisAndroidPlugin : StaticAnalysisPlugin() {
                                 buildVariant = applicationVariants.first { it.name.contains("Debug") }.name
                         )
                     }
-
+                    /**
+                     *  Task to run detekt checks.
+                     *
+                     * @param --only-diffs <branch or commit> if specified, only files modified
+                     * relative to this branch or commit will be checked. If specified without value
+                     * then current uncommited changes will be checked. If not specified all source files will be checked.
+                     * @see DetektLinter.getGitDiffFiles, 'git diff' for more info.
+                     * */
                     project.tasks.register("detektAnalysis") {
                         val detektLinter = linters.find { it is DetektLinter }
                                 ?: throw IllegalStateException("DetektLinter not found")