Add helper package for filesystem operations

Add package `filesystem` for file system related helper functions.

Add `MostRecentFileTimestamp` function to find the most recent file modification
timestamp of all files in a given directory.

pkg/filesystem/filesystem_suite_test.go

@@ -0,0 +1,36 @@
+// Copyright The Shipwright Contributors
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package filesystem_test
+
+import (
+	"os"
+	"testing"
+	"time"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+)
+
+func TestFilesystem(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "Filesystem Suite")
+}
+
+func withTempDir(f func(target string)) {
+	GinkgoHelper()
+
+	path, err := os.MkdirTemp(os.TempDir(), "filesystem")
+	Expect(err).ToNot(HaveOccurred())
+	defer os.RemoveAll(path)
+
+	f(path)
+}
+
+func writeTmpFile(parent string, atime time.Time, mtime time.Time) {
+	tmpFile, err := os.CreateTemp(parent, "test")
+	Expect(err).ToNot(HaveOccurred())
+	Expect(os.WriteFile(tmpFile.Name(), []byte("foobar"), os.FileMode(0644))).To(Succeed())
+	Expect(os.Chtimes(tmpFile.Name(), atime, mtime)).To(Succeed())
+}

pkg/filesystem/timestamps.go

@@ -0,0 +1,42 @@
+// Copyright The Shipwright Contributors
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package filesystem
+
+import (
+	"io/fs"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+func MostRecentFileTimestamp(root string) (result *time.Time, err error) {
+	err = filepath.WalkDir(root, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+
+		if d.IsDir() {
+			return nil
+		}
+
+		fi, err := os.Lstat(path)
+		if err != nil {
+			return err
+		}
+
+		var modTime = fi.ModTime()
+		switch {
+		case result == nil:
+			result = &modTime
+
+		case result.Before(modTime):
+			result = &modTime
+		}
+
+		return nil
+	})
+
+	return result, err
+}

pkg/filesystem/timestamps_test.go

@@ -0,0 +1,38 @@
+// Copyright The Shipwright Contributors
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package filesystem_test
+
+import (
+	"time"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+
+	. "github.com/shipwright-io/build/pkg/filesystem"
+)
+
+var _ = Describe("Timestamps", func() {
+	Context("Figure out timestamps recursively in a directory", func() {
+		It("should find the most recent timestamp in a given directory", func() {
+			var ref = time.Now()
+
+			withTempDir(func(target string) {
+				By("setting up a simple test sample", func() {
+					for i := 0; i < 10; i++ {
+						tmpTime := ref.AddDate(0, 0, -i)
+						writeTmpFile(target, tmpTime, tmpTime)
+					}
+				})
+
+				By("checking if finds the right timestamp", func() {
+					timestamp, err := MostRecentFileTimestamp(target)
+					Expect(err).ToNot(HaveOccurred())
+					Expect(timestamp).ToNot(BeNil())
+					Expect(*timestamp).To(BeTemporally("==", ref))
+				})
+			})
+		})
+	})
+})