Introduce merge.ff configuration handling

When the provided FastForwardStrategy is FastForwardStrategy.Default,
honor the merge.ff configuration setting.  When merge.ff=only, enable
fast-forward only mode; when merge.ff=false, enable no-ff mode.

1 files changed, 31 insertions, 0 deletions

diff --git a/LibGit2Sharp.Tests/MergeFixture.cs b/LibGit2Sharp.Tests/MergeFixture.cs
index 2fcf9c64..dc0b8560 100644
--- a/LibGit2Sharp.Tests/MergeFixture.cs
+++ b/LibGit2Sharp.Tests/MergeFixture.cs
@@ -472,6 +472,19 @@ namespace LibGit2Sharp.Tests
         }
 
         [Fact]
+        public void CanForceFastForwardMergeThroughConfig()
+        {
+            string path = CloneMergeTestRepo();
+            using (var repo = new Repository(path))
+            {
+                repo.Config.Set("merge.ff", "only");
+
+                Commit commitToMerge = repo.Branches["normal_merge"].Tip;
+                Assert.Throws<NonFastForwardException>(() => repo.Merge(commitToMerge, Constants.Signature, new MergeOptions()));
+            }
+        }
+
+        [Fact]
         public void CanMergeAndNotCommit()
         {
             string path = CloneMergeTestRepo();
@@ -509,6 +522,24 @@ namespace LibGit2Sharp.Tests
         }
 
         [Fact]
+        public void CanForceNonFastForwardMergeThroughConfig()
+        {
+            string path = CloneMergeTestRepo();
+            using (var repo = new Repository(path))
+            {
+                repo.Config.Set("merge.ff", "false");
+
+                Commit commitToMerge = repo.Branches["fast_forward"].Tip;
+
+                MergeResult result = repo.Merge(commitToMerge, Constants.Signature, new MergeOptions());
+
+                Assert.Equal(MergeStatus.NonFastForward, result.Status);
+                Assert.Equal("f58f780d5a0ae392efd4a924450b1bbdc0577d32", result.Commit.Id.Sha);
+                Assert.False(repo.Index.RetrieveStatus().Any());
+            }
+        }
+
+        [Fact]
         public void VerifyUpToDateMerge()
         {
             string path = CloneMergeTestRepo();