1 files changed, 110 insertions, 3 deletions
diff --git a/repository_test.go b/repository_test.go
index 51df845..b211f8c 100644
--- a/repository_test.go
+++ b/repository_test.go
@@ -82,7 +82,7 @@ func (s *RepositorySuite) TestInitWithInvalidDefaultBranch(c *C) {
 	c.Assert(err, NotNil)
 }
 
-func createCommit(c *C, r *Repository) {
+func createCommit(c *C, r *Repository) plumbing.Hash {
 	// Create a commit so there is a HEAD to check
 	wt, err := r.Worktree()
 	c.Assert(err, IsNil)
@@ -101,13 +101,14 @@ func createCommit(c *C, r *Repository) {
 		Email: "go-git@fake.local",
 		When:  time.Now(),
 	}
-	_, err = wt.Commit("test commit message", &CommitOptions{
+
+	h, err := wt.Commit("test commit message", &CommitOptions{
 		All:       true,
 		Author:    &author,
 		Committer: &author,
 	})
 	c.Assert(err, IsNil)
-
+	return h
 }
 
 func (s *RepositorySuite) TestInitNonStandardDotGit(c *C) {
@@ -439,6 +440,112 @@ func (s *RepositorySuite) TestCreateBranchAndBranch(c *C) {
 	c.Assert(branch.Merge, Equals, testBranch.Merge)
 }
 
+func (s *RepositorySuite) TestMergeFF(c *C) {
+	r, err := Init(memory.NewStorage(), memfs.New())
+	c.Assert(err, IsNil)
+	c.Assert(r, NotNil)
+
+	createCommit(c, r)
+	createCommit(c, r)
+	createCommit(c, r)
+	lastCommit := createCommit(c, r)
+
+	wt, err := r.Worktree()
+	c.Assert(err, IsNil)
+
+	targetBranch := plumbing.NewBranchReferenceName("foo")
+	err = wt.Checkout(&CheckoutOptions{
+		Hash:   lastCommit,
+		Create: true,
+		Branch: targetBranch,
+	})
+	c.Assert(err, IsNil)
+
+	createCommit(c, r)
+	fooHash := createCommit(c, r)
+
+	// Checkout the master branch so that we can try to merge foo into it.
+	err = wt.Checkout(&CheckoutOptions{
+		Branch: plumbing.Master,
+	})
+	c.Assert(err, IsNil)
+
+	head, err := r.Head()
+	c.Assert(err, IsNil)
+	c.Assert(head.Hash(), Equals, lastCommit)
+
+	targetRef := plumbing.NewHashReference(targetBranch, fooHash)
+	c.Assert(targetRef, NotNil)
+
+	err = r.Merge(*targetRef, MergeOptions{
+		Strategy: FastForwardMerge,
+	})
+	c.Assert(err, IsNil)
+
+	head, err = r.Head()
+	c.Assert(err, IsNil)
+	c.Assert(head.Hash(), Equals, fooHash)
+}
+
+func (s *RepositorySuite) TestMergeFF_Invalid(c *C) {
+	r, err := Init(memory.NewStorage(), memfs.New())
+	c.Assert(err, IsNil)
+	c.Assert(r, NotNil)
+
+	// Keep track of the first commit, which will be the
+	// reference to create the target branch so that we
+	// can simulate a non-ff merge.
+	firstCommit := createCommit(c, r)
+	createCommit(c, r)
+	createCommit(c, r)
+	lastCommit := createCommit(c, r)
+
+	wt, err := r.Worktree()
+	c.Assert(err, IsNil)
+
+	targetBranch := plumbing.NewBranchReferenceName("foo")
+	err = wt.Checkout(&CheckoutOptions{
+		Hash:   firstCommit,
+		Create: true,
+		Branch: targetBranch,
+	})
+
+	c.Assert(err, IsNil)
+
+	createCommit(c, r)
+	h := createCommit(c, r)
+
+	// Checkout the master branch so that we can try to merge foo into it.
+	err = wt.Checkout(&CheckoutOptions{
+		Branch: plumbing.Master,
+	})
+	c.Assert(err, IsNil)
+
+	head, err := r.Head()
+	c.Assert(err, IsNil)
+	c.Assert(head.Hash(), Equals, lastCommit)
+
+	targetRef := plumbing.NewHashReference(targetBranch, h)
+	c.Assert(targetRef, NotNil)
+
+	err = r.Merge(*targetRef, MergeOptions{
+		Strategy: MergeStrategy(10),
+	})
+	c.Assert(err, Equals, ErrUnsupportedMergeStrategy)
+
+	// Failed merge operations must not change HEAD.
+	head, err = r.Head()
+	c.Assert(err, IsNil)
+	c.Assert(head.Hash(), Equals, lastCommit)
+
+	err = r.Merge(*targetRef, MergeOptions{})
+	c.Assert(err, Equals, ErrFastForwardMergeNotPossible)
+
+	head, err = r.Head()
+	c.Assert(err, IsNil)
+	c.Assert(head.Hash(), Equals, lastCommit)
+}
+
 func (s *RepositorySuite) TestCreateBranchUnmarshal(c *C) {
 	r, _ := Init(memory.NewStorage(), nil)