Use crypto.sha1() instead of sha1sum command

pkg/ghost/types/branchspec.go

@@ -22,6 +22,7 @@ import (
 	"github.com/pfnet-research/git-ghost/pkg/ghost/git"
 	"github.com/pfnet-research/git-ghost/pkg/util"
 	"github.com/pfnet-research/git-ghost/pkg/util/errors"
+	"github.com/pfnet-research/git-ghost/pkg/util/hash"
 
 	multierror "github.com/hashicorp/go-multierror"
 	log "github.com/sirupsen/logrus"
@@ -243,7 +244,7 @@ func (bs DiffBranchSpec) CreateBranch(we WorkingEnv) (GhostBranch, errors.GitGho
 		}
 	}
 
-	hash, err := util.GenerateFileContentHash(tmpFile.Name())
+	hash, err := hash.GenerateFileContentHash(tmpFile.Name())
 	if err != nil {
 		return nil, errors.WithStack(err)
 	}

pkg/util/hash.go → pkg/util/hash/hash.go

@@ -12,22 +12,27 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package util
+package hash
 
 import (
-	"os/exec"
-	"strings"
+	"crypto/sha1"
+	"fmt"
+	"io"
+	"os"
 
 	"github.com/pfnet-research/git-ghost/pkg/util/errors"
 )
 
 func GenerateFileContentHash(filepath string) (string, errors.GitGhostError) {
-	// TODO: Use appropriate hash algorithm
-	cmd := exec.Command("sha1sum", "-b", filepath)
-	output, err := cmd.Output()
+	// ref: https://pkg.go.dev/crypto/sha1#example-New-File
+	f, err := os.Open(filepath)
 	if err != nil {
 		return "", errors.WithStack(err)
 	}
-	hash := strings.Split(string(output), " ")[0]
-	return hash, nil
+	defer f.Close()
+	h := sha1.New()
+	if _, err := io.Copy(h, f); err != nil {
+		return "", errors.WithStack(err)
+	}
+	return fmt.Sprintf("%x", h.Sum(nil)), nil
 }

pkg/util/hash/hash_test.go

@@ -0,0 +1,52 @@
+// Copyright 2019 Preferred Networks, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package hash_test
+
+import (
+	"os"
+	"os/exec"
+	"strings"
+	"testing"
+
+	"github.com/pfnet-research/git-ghost/pkg/util/hash"
+	"github.com/stretchr/testify/assert"
+)
+
+func calculateHashWithCommand(filepath string) (string, error) {
+	cmd := exec.Command("sha1sum", "-b", filepath)
+	output, err := cmd.Output()
+	if err != nil {
+		return "", err
+	}
+	hash := strings.Split(string(output), " ")[0]
+	return hash, nil
+}
+
+// Check compatibility so that patches generated by previous versions of git-ghost can be loaded
+func TestHashCompatibility(t *testing.T) {
+	tmpFile, err := os.CreateTemp(os.TempDir(), "tempfile-test-")
+	if err != nil {
+		t.Fatal(err)
+	}
+	oldHash, err := calculateHashWithCommand(tmpFile.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+	newHash, err := hash.GenerateFileContentHash(tmpFile.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+	assert.Equal(t, oldHash, newHash)
+}