Fix release notes issue when previous commit was a merge commit (#32)

CHANGELOG.md

@@ -2,6 +2,12 @@ Change Log
 ==========
 All notable changes to this project will be documented in this file.
 
+[Version 1.0.3 _(UNRELEASED)_](https://github.com/xmartlabs/android-snapshot-publisher/releases/tag/v1.0.3)
+---
+
+### Fixes
+- Fix release notes issue when previous commit was a merge commit(#31)
+
 [Version 1.0.2 _(2018-04-30)_](https://github.com/xmartlabs/android-snapshot-publisher/releases/tag/v1.0.2)
 ---
 

src/main/kotlin/com/xmartlabs/snapshotpublisher/utils/GitHelper.kt

@@ -25,7 +25,9 @@ internal object GitHelper {
     return proc.inputStream.bufferedReader().readText().trim()
   }
 
-  private fun getPreviousTag() = "git describe --tags --abbrev=0 HEAD^".execute()
+  private fun getPreviousTag() = "git describe --tags --abbrev=0 ${getPreviousCommitHash()}".execute()
+
+  private fun getPreviousCommitHash() = "git log --format=%H --skip 1 -1".execute()
 
   fun getCommitHash() = "git rev-parse --short HEAD".execute()
 
@@ -39,7 +41,7 @@ internal object GitHelper {
 
   private fun getHistoryRange(releaseNotesConfig: ReleaseNotesConfig): String {
     val startRange = if (releaseNotesConfig.includeHistorySinceLastTag) getPreviousTag() else null
-    val endRange = "HEAD" + if (releaseNotesConfig.includeLastCommitInHistory) "" else "^"
+    val endRange = if (releaseNotesConfig.includeLastCommitInHistory) "HEAD" else getPreviousCommitHash()
     return if (startRange.isNullOrBlank()) endRange else "$startRange..$endRange"
   }