Implement GetSHA256FromFS function to compute SHA256 hash from a filesystem. Add tests and sample files for validation

internal/util/cryptoutil/get_sha256_from_fs.go

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+package cryptoutil
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"io"
+	"io/fs"
+)
+
+// GetSHA256FromFS takes a fs.FS and returns a SHA256 hash of the combined contents
+// of all files in the filesystem.
+//
+// If there is an error, it returns an empty string.
+func GetSHA256FromFS(fsys fs.FS) string {
+	hash := sha256.New()
+
+	err := fs.WalkDir(fsys, ".", func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+
+		if d.IsDir() {
+			return nil
+		}
+
+		file, err := fsys.Open(path)
+		if err != nil {
+			return err
+		}
+		defer file.Close()
+
+		if _, err := io.Copy(hash, file); err != nil {
+			return err
+		}
+
+		return nil
+	})
+
+	if err != nil {
+		return ""
+	}
+
+	return hex.EncodeToString(hash.Sum(nil))
+}

internal/util/cryptoutil/get_sha256_from_fs_test.go

@@ -0,0 +1,32 @@
+package cryptoutil
+
+import (
+	"crypto/sha256"
+	"embed"
+	"encoding/hex"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+//go:embed get_sha256_from_fs_test_data/*
+var testFS embed.FS
+
+func TestGetSHA256FromFS_ValidFS(t *testing.T) {
+	hash := GetSHA256FromFS(testFS)
+	assert.NotEmpty(t, hash)
+
+	// To generate the expected hash, you must combine the contents of all the
+	// files in the test_data directory and calculate the SHA256 hash of the
+	// resulting string.
+	expectedHash := "d2c58b6783050a95542286a58250d4dc872877a6cf28610669516dcfacf954af"
+	assert.Equal(t, expectedHash, hash)
+}
+
+func TestGetSHA256FromFS_EmptyFS(t *testing.T) {
+	var emptyFS embed.FS
+	hash := GetSHA256FromFS(emptyFS)
+
+	expectedHash := sha256.New().Sum(nil)
+	assert.Equal(t, hex.EncodeToString(expectedHash), hash)
+}

internal/util/cryptoutil/get_sha256_from_fs_test_data/file1.txt

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+file 1 contents

internal/util/cryptoutil/get_sha256_from_fs_test_data/file2.txt

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+file 2 contents

internal/util/cryptoutil/get_sha256_from_fs_test_data/subfolder/subfolder/file3.txt

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+file 3 contents