diff --git a/commit.go b/commit.go
index 57e1a77..52f7c01 100644
--- a/commit.go
+++ b/commit.go
@@ -9,6 +9,7 @@ import "C"
 
 import (
 	"runtime"
+	"unsafe"
 )
 
 // Commit
@@ -70,3 +71,40 @@ func (c *Commit) ParentId(n uint) *Oid {
 func (c *Commit) ParentCount() uint {
 	return uint(C.git_commit_parentcount(c.cast_ptr))
 }
+
+func (c *Commit) Amend(refname string, author, committer *Signature, message string, tree *Tree) (*Oid, error) {
+	var cref *C.char
+	if refname == "" {
+		cref = nil
+	} else {
+		cref = C.CString(refname)
+		defer C.free(unsafe.Pointer(cref))
+	}
+
+	cmsg := C.CString(message)
+	defer C.free(unsafe.Pointer(cmsg))
+
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	authorSig, err := author.toC()
+	if err != nil {
+		return nil, err
+	}
+	defer C.git_signature_free(authorSig)
+
+	committerSig, err := committer.toC()
+	if err != nil {
+		return nil, err
+	}
+	defer C.git_signature_free(committerSig)
+
+	oid := new(Oid)
+
+	cerr := C.git_commit_amend(oid.toC(), c.cast_ptr, cref, authorSig, committerSig, nil, cmsg, tree.cast_ptr)
+	if cerr < 0 {
+		return nil, MakeGitError(cerr)
+	}
+
+	return oid, nil
+}
diff --git a/diff.go b/diff.go
index 63fa867..23469f2 100644
--- a/diff.go
+++ b/diff.go
@@ -595,3 +595,53 @@ func (v *Repository) DiffTreeToWorkdir(oldTree *Tree, opts *DiffOptions) (*Diff,
 	}
 	return newDiffFromC(diffPtr), nil
 }
+
+func (v *Repository) DiffTreeToWorkdirWithIndex(oldTree *Tree, opts *DiffOptions) (*Diff, error) {
+	var diffPtr *C.git_diff
+	var oldPtr *C.git_tree
+
+	if oldTree != nil {
+		oldPtr = oldTree.cast_ptr
+	}
+
+	copts, notifyData := diffOptionsToC(opts)
+	defer freeDiffOptions(copts)
+
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	ecode := C.git_diff_tree_to_workdir_with_index(&diffPtr, v.ptr, oldPtr, copts)
+	if ecode < 0 {
+		return nil, MakeGitError(ecode)
+	}
+
+	if notifyData != nil && notifyData.Diff != nil {
+		return notifyData.Diff, nil
+	}
+	return newDiffFromC(diffPtr), nil
+}
+
+func (v *Repository) DiffIndexToWorkdir(index *Index, opts *DiffOptions) (*Diff, error) {
+	var diffPtr *C.git_diff
+	var indexPtr *C.git_index
+
+	if index != nil {
+		indexPtr = index.ptr
+	}
+
+	copts, notifyData := diffOptionsToC(opts)
+	defer freeDiffOptions(copts)
+
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	ecode := C.git_diff_index_to_workdir(&diffPtr, v.ptr, indexPtr, copts)
+	if ecode < 0 {
+		return nil, MakeGitError(ecode)
+	}
+
+	if notifyData != nil && notifyData.Diff != nil {
+		return notifyData.Diff, nil
+	}
+	return newDiffFromC(diffPtr), nil
+}
diff --git a/index.go b/index.go
index 6b90758..9f37f33 100644
--- a/index.go
+++ b/index.go
@@ -287,6 +287,7 @@ func (v *Index) HasConflicts() bool {
 	return C.git_index_has_conflicts(v.ptr) != 0
 }
 
+// FIXME: this might return an error
 func (v *Index) CleanupConflicts() {
 	C.git_index_conflict_cleanup(v.ptr)
 }