remove renames with same source and destination

mmv.go

@@ -61,6 +61,12 @@ func buildRenames(files map[string]string) ([]rename, error) {
 		}
 		revs[dst] = src
 	}
+	for src, dst := range files {
+		if src == dst {
+			delete(files, src)
+			delete(revs, dst)
+		}
+	}
 	var i int
 	for _, dst := range files {
 		if vs[dst] > 0 {

mmv_test.go

@@ -198,6 +198,30 @@ func TestRename(t *testing.T) {
 			},
 			err: &sameDestinationError{"baz"},
 		},
+		{
+			name: "same source and destination",
+			files: map[string]string{
+				"foo/": "foo",
+				"bar/": "bar",
+			},
+			cnt: 0,
+			contents: map[string]string{
+				"foo": "0",
+				"bar": "1",
+			},
+			expected: map[string]string{
+				"foo": "0",
+				"bar": "1",
+			},
+		},
+		{
+			name: "same source and destination with error",
+			files: map[string]string{
+				"foo/": "foo/",
+				"bar/": "foo",
+			},
+			err: &sameDestinationError{"foo"},
+		},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {