Consider the fact that Git trims all lines in commit message IDEA-175002

plugins/git4idea/src/git4idea/rebase/GitRewordOperation.kt

@@ -27,6 +27,7 @@ import com.intellij.openapi.progress.ProgressIndicator
 import com.intellij.openapi.progress.ProgressManager
 import com.intellij.openapi.progress.Task
 import com.intellij.openapi.project.Project
+import com.intellij.openapi.util.text.StringUtil
 import com.intellij.openapi.vcs.VcsNotifier
 import com.intellij.openapi.vcs.VcsNotifier.STANDARD_NOTIFICATION
 import com.intellij.util.containers.MultiMap
@@ -118,7 +119,7 @@ class GitRewordOperation(private val repository: GitRepository,
       return null
     }
     val newCommit = newCommits.last()
-    if (newCommit.fullMessage != newMessage) {
+    if (!StringUtil.equalsIgnoreWhitespaces(newCommit.fullMessage, newMessage)) {
       LOG.error("Couldn't find the reworded commit. Expected message: \n[$newMessage]\nActual message: \n[${newCommit.fullMessage}]")
       return null
     }

plugins/git4idea/tests/git4idea/rebase/GitRewordTest.kt

@@ -15,6 +15,7 @@
  */
 package git4idea.rebase
 
+import com.intellij.openapi.util.text.StringUtil
 import git4idea.test.GitSingleRepoTest
 import git4idea.test.assertLatestHistory
 import git4idea.test.file
@@ -90,4 +91,16 @@ class GitRewordTest : GitSingleRepoTest() {
     )
     assertErrorNotification("Can't Undo Reword", "Commit has already been pushed to origin/master")
   }
+
+  // IDEA-175002
+  fun `test reword with trailing spaces`() {
+    val commit = file("a").create("initial").addCommit("Wrong message").details()
+
+    val newMessage = "Subject with trailing spaces  \n\nBody \nwith \nspaces."
+    GitRewordOperation(myRepo, commit, newMessage).execute()
+
+    val actualMessage = git("log HEAD --no-walk --pretty=%B")
+    assertTrue("Message reworded incorrectly. Expected:\n[$newMessage] Actual:\n[$actualMessage]",
+               StringUtil.equalsIgnoreWhitespaces(newMessage, actualMessage))
+  }
 }