Check the same lines have been added or removed

The --indent-heuristic option should create patches that add or remove
the same lines, but potentially in a different order.

Author: jcansdale

LibGit2Sharp.Tests/DiffBlobToBlobFixture.cs

@@ -1,4 +1,5 @@
 using System.IO;
+using System.Linq;
 using System.Text;
 using LibGit2Sharp.Tests.TestHelpers;
 using Xunit;
@@ -163,10 +164,10 @@ public void ComparingBlobsWithNoSpacesAndIndentHeuristicOptionMakesADifference()
                 ContentChanges changes1 = repo.Diff.Compare(oldBlob, newBlob, indentHeuristicOption);
 
                 Assert.NotEqual(changes0.Patch, changes1.Patch);
+                Assert.Equal(CanonicalChangedLines(changes0), CanonicalChangedLines(changes1));
             }
         }
 
-
         [Fact]
         public void ComparingBlobsWithNoSpacesIndentHeuristicOptionMakesNoDifference()
         {
@@ -200,5 +201,11 @@ public void ComparingBlobsWithNoSpacesIndentHeuristicOptionMakesNoDifference()
                 Assert.Equal(changes0.Patch, changes1.Patch);
             }
         }
+
+        static string CanonicalChangedLines(ContentChanges changes)
+        {
+            // Create an ordered representation of lines that have been added or removed
+            return string.Join("\n", changes.Patch.Split('\n').Where(l => l.StartsWith("+") || l.StartsWith("-")).OrderBy(l => l));
+        }
     }
 }