Add positive tests for BinaryFragment#Apply

Covers basic literal and delta application. Input files were created by
using dd and the 'conv=notrunc' option to modify sections of files
created from /dev/urandom. All file start with two null bytes to
convince Git they are binary.

gitdiff/apply.go

···
 		if err := applyBinaryDeltaFragment(dst, fullSrc, f.Data); err != nil {
 			return applyError(err)
 		}
+	default:
+		return applyError(fmt.Errorf("unsupported binary patch method: %v", f.Method))
 	}
-	return applyError(fmt.Errorf("unsupported binary patch method: %v", f.Method))
+
+	return nil
 }
 
 func applyBinaryDeltaFragment(dst io.Writer, src, frag []byte) error {

gitdiff/apply_test.go

···
 		})
 	}
 }
+
+func TestBinaryFragmentApply(t *testing.T) {
+	tests := map[string]struct {
+		File      string
+		SrcFile   string
+		PatchFile string
+		DstFile   string
+
+		Err error
+	}{
+		"literalCreate": {File: "bin_fragment_literal_create"},
+		"literalModify": {File: "bin_fragment_literal_modify"},
+		"deltaModify":   {File: "bin_fragment_delta_modify"},
+	}
+
+	loadFile := func(name, defaultName, ext string) []byte {
+		if name == "" {
+			name = defaultName
+		}
+		d, err := ioutil.ReadFile(filepath.Join("testdata", "apply", name+"."+ext))
+		if err != nil {
+			t.Fatalf("failed to read %s file: %v", ext, err)
+		}
+		return d
+	}
+
+	for name, test := range tests {
+		t.Run(name, func(t *testing.T) {
+			src := loadFile(test.SrcFile, test.File, "src")
+			patch := loadFile(test.PatchFile, test.File, "patch")
+
+			var result []byte
+			if test.Err == nil {
+				result = loadFile(test.DstFile, test.File, "dst")
+			}
+
+			files, _, err := Parse(bytes.NewReader(patch))
+			if err != nil {
+				t.Fatalf("failed to parse patch file: %v", err)
+			}
+
+			frag := files[0].BinaryFragment
+
+			var dst bytes.Buffer
+			err = frag.Apply(&dst, bytes.NewReader(src))
+			if test.Err != nil {
+				if err == nil {
+					t.Fatalf("expected error applying fragment, but got nil")
+				}
+				if !errors.Is(err, test.Err) {
+					t.Fatalf("incorrect apply error: expected: %T (%v), actual: %T (%v)", test.Err, test.Err, err, err)
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("unexpected error applying fragment: %v", err)
+			}
+
+			if !bytes.Equal(result, dst.Bytes()) {
+				t.Errorf("incorrect result after apply\nexpected:\n%x\nactual:\n%x", result, dst.Bytes())
+			}
+		})
+	}
+}

gitdiff/testdata/apply/bin_fragment_delta_modify.patch

···
+diff --git a/gitdiff/testdata/apply/bin_fragment_delta_modify.src b/gitdiff/testdata/apply/bin_fragment_delta_modify.src
+GIT binary patch
+delta 172
+zcmV;d08{^f2)qc8AP{I3VQ>J`s>wb0HU+h#6w8q?tUO~cHmDjZi2<8yZ9XmKhhMdo
+zWu(4bg|8QwzZ|1e*rL4P#)`Fen<n~ik=E?$qG6?hzJ6$u{l5W#?uwHb0q6w)00000
+zlLZ3%0RfW%1N%UMJ{~Z~0@X${&1Kk#98tb3==a{J7A;`O`v&<T@514_mvMTz72b#n
+atf$#NLoPbNe?RPFJVt1aCFGoQbiKD!OHgJ2
+
+delta 112
+zcmV-$0FVE?2!IHXAP~DY<7&llQfwqYA%tL<sR@xVtUMD;+4ZG>XTQ5=J2y;^BfB}4
+zWkisH791|vOVl5e-@^VLX0s~Ky_UyN!3;CgPr>Edj0j+0gOSwSsFsr$0q6zUJph<q
+SlLZ3%0XmZb1N#I__7UCuR5Dxu
+

gitdiff/testdata/apply/bin_fragment_literal_create.patch

···
+diff --git a/gitdiff/testdata/apply/bin_fragment_literal_create.src b/gitdiff/testdata/apply/bin_fragment_literal_create.src
+GIT binary patch
+literal 32
+ocmZQzU`lR_IpTEv<rOIzfy0`|3>L*`JUiBtu5<US@-j_*0M$he#sB~S
+
+literal 0
+HcmV?d00001
+

gitdiff/testdata/apply/bin_fragment_literal_modify.patch

···
+diff --git a/gitdiff/testdata/apply/bin_fragment_literal_modify.src b/gitdiff/testdata/apply/bin_fragment_literal_modify.src
+GIT binary patch
+literal 32
+ocmZQzU`lR_IpTEv<rOIzfy0_p?@r&O@$6Vny3XCR%F8tM0pJ`CjQ{`u
+
+literal 32
+ocmZQzU`lR_IpTEv<rOIzfy0`|3>L*`JUiBtu5<US@-j_*0M$he#sB~S
+