Add parentBranch configuration to support CI environments with detached HEAD

README.md

@@ -98,6 +98,9 @@ affectedModuleDetector {
     buildAllWhenNoProjectsChanged = true // default is true
     includeUncommitted = true
     top = "HEAD"
+    specifiedBranch = "main"
+    specifiedRawCommitSha = "abc123"
+    parentBranch = "main" // Optional: specify parent branch for ForkCommit comparison
     customTasks = [
         new AffectedModuleConfiguration.CustomTask(
             "runDetektByImpact",
@@ -114,6 +117,7 @@ affectedModuleDetector {
  - `logFolder`: A folder to output the log file in
  - `specifiedBranch`: A branch to specify changes against. Must be used in combination with configuration `compareFrom = "SpecifiedBranchCommit"` 
  - `specifiedRawCommitSha`: A raw commit SHA to specify changes against. Must be used in combination with configuration `compareFrom = "SpecifiedRawCommitSha"`
+ - `parentBranch`: A branch to specify as the parent branch for ForkCommit comparison. If not provided, ForkCommit will try to detect it automatically.
  - `ignoredFiles`: A set of files that will be filtered out of the list of changed files retrieved by git. 
  - `buildAllWhenNoProjectsChanged`: If true, the plugin will build all projects when no projects are considered affected.
  - `compareFrom`: A commit to compare the branch changes against. Can be either:
@@ -225,7 +229,6 @@ which is implementing the [AffectedModuleTaskType](https://github.com/dropbox/Af
 
 ```groovy
 // ... 
-
 affectedModuleDetector {
      // ...
      customTasks = [
@@ -263,3 +266,4 @@ Special thanks to the AndroidX team for originally developing this project at ht
     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     See the License for the specific language governing permissions and
     limitations under the License.
+

affectedmoduledetector/src/main/kotlin/com/dropbox/affectedmoduledetector/AffectedModuleConfiguration.kt

@@ -84,6 +84,8 @@ class AffectedModuleConfiguration : Serializable {
 
     var specifiedRawCommitSha: String? = null
 
+    var parentBranch: String? = null
+
     var compareFrom: String = "PreviousCommit"
         set(value) {
             val commitShaProviders = listOf(

affectedmoduledetector/src/main/kotlin/com/dropbox/affectedmoduledetector/AffectedModuleDetector.kt

@@ -207,7 +207,8 @@ abstract class AffectedModuleDetector(protected val logger: Logger?) {
                     specifiedBranch = config.specifiedBranch,
                     specifiedSha = config.specifiedRawCommitSha,
                     top = config.top,
-                    includeUncommitted = config.includeUncommitted
+                    includeUncommitted = config.includeUncommitted,
+                    parentBranch = config.parentBranch
                 ),
                 ignoredFiles = config.ignoredFiles
             )

affectedmoduledetector/src/main/kotlin/com/dropbox/affectedmoduledetector/GitClient.kt

@@ -232,7 +232,7 @@ internal abstract class GitChangedFilesSource :
         val specifiedSha = parameters.commitShaProvider.specifiedSha
         val type = when (parameters.commitShaProvider.type) {
             "PreviousCommit" -> PreviousCommit()
-            "ForkCommit" -> ForkCommit()
+            "ForkCommit" -> ForkCommit(parameters.commitShaProvider.parentBranch)
             "SpecifiedBranchCommit" -> {
                 requireNotNull(specifiedBranch) {
                     "Specified branch must be defined"

affectedmoduledetector/src/main/kotlin/com/dropbox/affectedmoduledetector/commitshaproviders/CommitShaProvider.kt

@@ -13,5 +13,6 @@ data class CommitShaProviderConfiguration(
     val specifiedBranch: String? = null,
     val specifiedSha: String? = null,
     val top: Sha,
-    val includeUncommitted: Boolean
+    val includeUncommitted: Boolean,
+    val parentBranch: String? = null
 ) : Serializable

affectedmoduledetector/src/main/kotlin/com/dropbox/affectedmoduledetector/commitshaproviders/ForkCommit.kt

@@ -3,11 +3,11 @@ package com.dropbox.affectedmoduledetector.commitshaproviders
 import com.dropbox.affectedmoduledetector.GitClient
 import com.dropbox.affectedmoduledetector.Sha
 
-class ForkCommit : CommitShaProvider {
+class ForkCommit(private val providedParentBranch: String? = null) : CommitShaProvider {
     override fun get(commandRunner: GitClient.CommandRunner): Sha {
         val currentBranch = commandRunner.executeAndParseFirst(CURRENT_BRANCH_CMD)
 
-        val parentBranch = commandRunner.executeAndParse(SHOW_ALL_BRANCHES_CMD)
+        val parentBranch = providedParentBranch ?: commandRunner.executeAndParse(SHOW_ALL_BRANCHES_CMD)
             .firstOrNull { !it.contains(currentBranch) && it.contains("*") }
             ?.substringAfter("[")
             ?.substringBefore("]")

affectedmoduledetector/src/test/kotlin/com/dropbox/affectedmoduledetector/AffectedModuleConfigurationTest.kt

@@ -376,4 +376,20 @@ class AffectedModuleConfigurationTest {
         // THEN
         assertFalse(actual)
     }
+
+    @Test
+    fun `GIVEN AffectedModuleConfiguration WHEN parentBranch is set THEN value is returned`() {
+        val parentBranch = "main"
+
+        config.parentBranch = parentBranch
+
+        val actual = config.parentBranch
+        assertThat(actual).isEqualTo(parentBranch)
+    }
+
+    @Test
+    fun `GIVEN AffectedModuleConfiguration WHEN parentBranch is not set THEN null is returned`() {
+        val actual = config.parentBranch
+        assertThat(actual).isNull()
+    }
 }

affectedmoduledetector/src/test/kotlin/com/dropbox/affectedmoduledetector/commitshaproviders/ForkCommitTest.kt

@@ -75,4 +75,17 @@ class ForkCommitTest {
 
         assertThat(actual).isEqualTo("commit-sha")
     }
+
+    @Test
+    fun givenProvidedParentBranch_whenGetCommitSha_thenVerifyExactCommand() {
+        val providedParentBranch = "abc"
+        val forkCommitWithParent = ForkCommit(providedParentBranch)
+
+        commandRunner.addReply(ForkCommit.CURRENT_BRANCH_CMD, "feature")
+        commandRunner.addReply("git merge-base feature abc", "commit-sha")
+
+        forkCommitWithParent.get(commandRunner)
+
+        assertThat(commandRunner.executedCommands).contains("git merge-base feature abc")
+    }
 }

affectedmoduledetector/src/test/kotlin/com/dropbox/affectedmoduledetector/mocks/MockCommandRunner.kt

@@ -5,26 +5,31 @@ import com.dropbox.affectedmoduledetector.GitClient
 
 internal class MockCommandRunner(private val logger: FileLogger) : GitClient.CommandRunner {
     private val replies = mutableMapOf<String, List<String>>()
+    private val _executedCommands = mutableListOf<String>()
+    val executedCommands: List<String> get() = _executedCommands
 
     fun addReply(command: String, response: String) {
         logger.info("add reply. cmd: $command response: $response")
         replies[command] = response.split(System.lineSeparator())
     }
 
     override fun execute(command: String): String {
+        _executedCommands.add(command)
         return replies.getOrDefault(command, emptyList())
             .joinToString(System.lineSeparator()).also {
                 logger.info("cmd: $command response: $it")
             }
     }
 
     override fun executeAndParse(command: String): List<String> {
+        _executedCommands.add(command)
         return replies.getOrDefault(command, emptyList()).also {
             logger.info("cmd: $command response: $it")
         }
     }
 
     override fun executeAndParseFirst(command: String): String {
+        _executedCommands.add(command)
         return replies.getOrDefault(command, emptyList()).first().also {
             logger.info("cmd: $command response: $it")
         }