From e13e5a7d43ef3905a6cf32a7aa4681a5a7984997 Mon Sep 17 00:00:00 2001
From: Aleksey Pivovarov <AMPivovarov@gmail.com>
Date: Mon, 5 Sep 2016 13:01:12 +0300
Subject: [PATCH] git: fix "annotate previous revision" for renamed files

In some cases (ex: when a file was split into two files), `git log` might detect more renames than `git blame`.

In this case we will fallback to the old history-based approach.
This might be not particulary right (ex: in tricky cases with multiple renames in multiple branches), but works good enough in general.
---
 .../git4idea/annotate/GitFileAnnotation.java  | 23 ++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/plugins/git4idea/src/git4idea/annotate/GitFileAnnotation.java b/plugins/git4idea/src/git4idea/annotate/GitFileAnnotation.java
index 93bb1f47168f..1c5e1e2fa72e 100644
--- a/plugins/git4idea/src/git4idea/annotate/GitFileAnnotation.java
+++ b/plugins/git4idea/src/git4idea/annotate/GitFileAnnotation.java
@@ -38,6 +38,7 @@ import git4idea.GitFileRevision;
 import git4idea.GitRevisionNumber;
 import git4idea.GitVcs;
 import git4idea.i18n.GitBundle;
+import gnu.trove.TObjectIntHashMap;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -51,6 +52,7 @@ public class GitFileAnnotation extends FileAnnotation {
 
   @NotNull private final List<LineInfo> myLines;
   @Nullable private List<VcsFileRevision> myRevisions;
+  @Nullable private TObjectIntHashMap<VcsRevisionNumber> myRevisionMap;
 
   private final LineAnnotationAspect DATE_ASPECT = new GitAnnotationAspect(LineAnnotationAspect.DATE, true) {
     @Override
@@ -113,6 +115,11 @@ public class GitFileAnnotation extends FileAnnotation {
 
   public void setRevisions(@NotNull List<VcsFileRevision> revisions) {
     myRevisions = revisions;
+
+    myRevisionMap = new TObjectIntHashMap<>();
+    for (int i = 0; i < myRevisions.size(); i++) {
+      myRevisionMap.put(myRevisions.get(i).getRevisionNumber(), i);
+    }
   }
 
   @Override
@@ -292,7 +299,21 @@ public class GitFileAnnotation extends FileAnnotation {
       @Override
       public VcsFileRevision getPreviousRevision(int lineNumber) {
         LineInfo lineInfo = getLineInfo(lineNumber);
-        return lineInfo != null ? lineInfo.getPreviousFileRevision() : null;
+        if (lineInfo == null) return null;
+
+        VcsFileRevision previousFileRevision = lineInfo.getPreviousFileRevision();
+        if (previousFileRevision != null) return previousFileRevision;
+
+        GitRevisionNumber revisionNumber = lineInfo.getRevisionNumber();
+        if (myRevisions != null && myRevisionMap != null &&
+            myRevisionMap.contains(revisionNumber)) {
+          int index = myRevisionMap.get(revisionNumber);
+          if (index + 1 < myRevisions.size()) {
+            return myRevisions.get(index + 1);
+          }
+        }
+
+        return null;
       }
 
       @Nullable