Add '-L' option for cp

Fixes #16555

Original docker `cp` always copy symbol link itself instead of target,
now we provide '-L' option to allow docker to follow symbol link to real
target.

Signed-off-by: Zhang Wei <zhangwei555@huawei.com>

archive/changes_test.go

@@ -63,6 +63,9 @@ func createSampleDir(t *testing.T, root string) {
 		{Regular, "dir4/file3-2", "file4-2\n", 0666},
 		{Symlink, "symlink1", "target1", 0666},
 		{Symlink, "symlink2", "target2", 0666},
+		{Symlink, "symlink3", root + "/file1", 0666},
+		{Symlink, "symlink4", root + "/symlink3", 0666},
+		{Symlink, "dirSymlink", root + "/dir1", 0740},
 	}
 
 	now := time.Now()

archive/copy.go

@@ -135,30 +135,17 @@ type CopyInfo struct {
 // operation. The given path should be an absolute local path. A source path
 // has all symlinks evaluated that appear before the last path separator ("/"
 // on Unix). As it is to be a copy source, the path must exist.
-func CopyInfoSourcePath(path string) (CopyInfo, error) {
+func CopyInfoSourcePath(path string, followLink bool) (CopyInfo, error) {
-	// Split the given path into its Directory and Base components. We will
+	// normalize the file path and then evaluate the symbol link
-	// evaluate symlinks in the directory component then append the base.
+	// we will use the target file instead of the symbol link if
+	// followLink is set
 	path = normalizePath(path)
-	dirPath, basePath := filepath.Split(path)
 
-	resolvedDirPath, err := filepath.EvalSymlinks(dirPath)
+	resolvedPath, rebaseName, err := ResolveHostSourcePath(path, followLink)
 	if err != nil {
 		return CopyInfo{}, err
 	}
 
-	// resolvedDirPath will have been cleaned (no trailing path separators) so
-	// we can manually join it with the base path element.
-	resolvedPath := resolvedDirPath + string(filepath.Separator) + basePath
-
-	var rebaseName string
-	if hasTrailingPathSeparator(path) && filepath.Base(path) != filepath.Base(resolvedPath) {
-		// In the case where the path had a trailing separator and a symlink
-		// evaluation has changed the last path component, we will need to
-		// rebase the name in the archive that is being copied to match the
-		// originally requested name.
-		rebaseName = filepath.Base(path)
-	}
-
 	stat, err := os.Lstat(resolvedPath)
 	if err != nil {
 		return CopyInfo{}, err
@@ -279,7 +266,10 @@ func PrepareArchiveCopy(srcContent Reader, srcInfo, dstInfo CopyInfo) (dstDir st
 		// The destination exists as some type of file and the source content
 		// is also a file. The source content entry will have to be renamed to
 		// have a basename which matches the destination path's basename.
-		return dstDir, rebaseArchiveEntries(srcContent, srcBase, dstBase), nil
+		if len(srcInfo.RebaseName) != 0 {
+			srcBase = srcInfo.RebaseName
+		}
+		return dstDir, RebaseArchiveEntries(srcContent, srcBase, dstBase), nil
 	case srcInfo.IsDir:
 		// The destination does not exist and the source content is an archive
 		// of a directory. The archive should be extracted to the parent of
@@ -287,7 +277,10 @@ func PrepareArchiveCopy(srcContent Reader, srcInfo, dstInfo CopyInfo) (dstDir st
 		// created as a result should take the name of the destination path.
 		// The source content entries will have to be renamed to have a
 		// basename which matches the destination path's basename.
-		return dstDir, rebaseArchiveEntries(srcContent, srcBase, dstBase), nil
+		if len(srcInfo.RebaseName) != 0 {
+			srcBase = srcInfo.RebaseName
+		}
+		return dstDir, RebaseArchiveEntries(srcContent, srcBase, dstBase), nil
 	case assertsDirectory(dstInfo.Path):
 		// The destination does not exist and is asserted to be created as a
 		// directory, but the source content is not a directory. This is an
@@ -301,14 +294,17 @@ func PrepareArchiveCopy(srcContent Reader, srcInfo, dstInfo CopyInfo) (dstDir st
 		// to be created when the archive is extracted and the source content
 		// entry will have to be renamed to have a basename which matches the
 		// destination path's basename.
-		return dstDir, rebaseArchiveEntries(srcContent, srcBase, dstBase), nil
+		if len(srcInfo.RebaseName) != 0 {
+			srcBase = srcInfo.RebaseName
+		}
+		return dstDir, RebaseArchiveEntries(srcContent, srcBase, dstBase), nil
 	}
 
 }
 
-// rebaseArchiveEntries rewrites the given srcContent archive replacing
+// RebaseArchiveEntries rewrites the given srcContent archive replacing
 // an occurrence of oldBase with newBase at the beginning of entry names.
-func rebaseArchiveEntries(srcContent Reader, oldBase, newBase string) Archive {
+func RebaseArchiveEntries(srcContent Reader, oldBase, newBase string) Archive {
 	if oldBase == string(os.PathSeparator) {
 		// If oldBase specifies the root directory, use an empty string as
 		// oldBase instead so that newBase doesn't replace the path separator
@@ -355,7 +351,7 @@ func rebaseArchiveEntries(srcContent Reader, oldBase, newBase string) Archive {
 // CopyResource performs an archive copy from the given source path to the
 // given destination path. The source path MUST exist and the destination
 // path's parent directory must exist.
-func CopyResource(srcPath, dstPath string) error {
+func CopyResource(srcPath, dstPath string, followLink bool) error {
 	var (
 		srcInfo CopyInfo
 		err     error
@@ -369,7 +365,7 @@ func CopyResource(srcPath, dstPath string) error {
 	srcPath = PreserveTrailingDotOrSeparator(filepath.Clean(srcPath), srcPath)
 	dstPath = PreserveTrailingDotOrSeparator(filepath.Clean(dstPath), dstPath)
 
-	if srcInfo, err = CopyInfoSourcePath(srcPath); err != nil {
+	if srcInfo, err = CopyInfoSourcePath(srcPath, followLink); err != nil {
 		return err
 	}
 
@@ -405,3 +401,58 @@ func CopyTo(content Reader, srcInfo CopyInfo, dstPath string) error {
 
 	return Untar(copyArchive, dstDir, options)
 }
+
+// ResolveHostSourcePath decides real path need to be copied with parameters such as
+// whether to follow symbol link or not, if followLink is true, resolvedPath will return
+// link target of any symbol link file, else it will only resolve symlink of directory
+// but return symbol link file itself without resolving.
+func ResolveHostSourcePath(path string, followLink bool) (resolvedPath, rebaseName string, err error) {
+	if followLink {
+		resolvedPath, err = filepath.EvalSymlinks(path)
+		if err != nil {
+			return
+		}
+
+		resolvedPath, rebaseName = GetRebaseName(path, resolvedPath)
+	} else {
+		dirPath, basePath := filepath.Split(path)
+
+		// if not follow symbol link, then resolve symbol link of parent dir
+		var resolvedDirPath string
+		resolvedDirPath, err = filepath.EvalSymlinks(dirPath)
+		if err != nil {
+			return
+		}
+		// resolvedDirPath will have been cleaned (no trailing path separators) so
+		// we can manually join it with the base path element.
+		resolvedPath = resolvedDirPath + string(filepath.Separator) + basePath
+		if hasTrailingPathSeparator(path) && filepath.Base(path) != filepath.Base(resolvedPath) {
+			rebaseName = filepath.Base(path)
+		}
+	}
+	return resolvedPath, rebaseName, nil
+}
+
+// GetRebaseName normalizes and compares path and resolvedPath,
+// return completed resolved path and rebased file name
+func GetRebaseName(path, resolvedPath string) (string, string) {
+	// linkTarget will have been cleaned (no trailing path separators and dot) so
+	// we can manually join it with them
+	var rebaseName string
+	if specifiesCurrentDir(path) && !specifiesCurrentDir(resolvedPath) {
+		resolvedPath += string(filepath.Separator) + "."
+	}
+
+	if hasTrailingPathSeparator(path) && !hasTrailingPathSeparator(resolvedPath) {
+		resolvedPath += string(filepath.Separator)
+	}
+
+	if filepath.Base(path) != filepath.Base(resolvedPath) {
+		// In the case where the path had a trailing separator and a symlink
+		// evaluation has changed the last path component, we will need to
+		// rebase the name in the archive that is being copied to match the
+		// originally requested name.
+		rebaseName = filepath.Base(path)
+	}
+	return resolvedPath, rebaseName
+}

archive/copy_test.go

@@ -120,9 +120,15 @@ func logDirContents(t *testing.T, dirPath string) {
 }
 
 func testCopyHelper(t *testing.T, srcPath, dstPath string) (err error) {
-	t.Logf("copying from %q to %q", srcPath, dstPath)
+	t.Logf("copying from %q to %q (not follow symbol link)", srcPath, dstPath)
 
-	return CopyResource(srcPath, dstPath)
+	return CopyResource(srcPath, dstPath, false)
+}
+
+func testCopyHelperFSym(t *testing.T, srcPath, dstPath string) (err error) {
+	t.Logf("copying from %q to %q (follow symbol link)", srcPath, dstPath)
+
+	return CopyResource(srcPath, dstPath, true)
 }
 
 // Basic assumptions about SRC and DST:
@@ -138,7 +144,7 @@ func TestCopyErrSrcNotExists(t *testing.T) {
 	tmpDirA, tmpDirB := getTestTempDirs(t)
 	defer removeAllPaths(tmpDirA, tmpDirB)
 
-	if _, err := CopyInfoSourcePath(filepath.Join(tmpDirA, "file1")); !os.IsNotExist(err) {
+	if _, err := CopyInfoSourcePath(filepath.Join(tmpDirA, "file1"), false); !os.IsNotExist(err) {
 		t.Fatalf("expected IsNotExist error, but got %T: %s", err, err)
 	}
 }
@@ -152,7 +158,7 @@ func TestCopyErrSrcNotDir(t *testing.T) {
 	// Load A with some sample files and directories.
 	createSampleDir(t, tmpDirA)
 
-	if _, err := CopyInfoSourcePath(joinTrailingSep(tmpDirA, "file1")); !isNotDir(err) {
+	if _, err := CopyInfoSourcePath(joinTrailingSep(tmpDirA, "file1"), false); !isNotDir(err) {
 		t.Fatalf("expected IsNotDir error, but got %T: %s", err, err)
 	}
 }
@@ -286,6 +292,27 @@ func TestCopyCaseA(t *testing.T) {
 	if err = fileContentsEqual(t, srcPath, dstPath); err != nil {
 		t.Fatal(err)
 	}
+	os.Remove(dstPath)
+
+	symlinkPath := filepath.Join(tmpDirA, "symlink3")
+	symlinkPath1 := filepath.Join(tmpDirA, "symlink4")
+	linkTarget := filepath.Join(tmpDirA, "file1")
+
+	if err = testCopyHelperFSym(t, symlinkPath, dstPath); err != nil {
+		t.Fatalf("unexpected error %T: %s", err, err)
+	}
+
+	if err = fileContentsEqual(t, linkTarget, dstPath); err != nil {
+		t.Fatal(err)
+	}
+	os.Remove(dstPath)
+	if err = testCopyHelperFSym(t, symlinkPath1, dstPath); err != nil {
+		t.Fatalf("unexpected error %T: %s", err, err)
+	}
+
+	if err = fileContentsEqual(t, linkTarget, dstPath); err != nil {
+		t.Fatal(err)
+	}
 }
 
 // B. SRC specifies a file and DST (with trailing path separator) doesn't
@@ -310,6 +337,16 @@ func TestCopyCaseB(t *testing.T) {
 	if err != ErrDirNotExists {
 		t.Fatalf("expected ErrDirNotExists error, but got %T: %s", err, err)
 	}
+
+	symlinkPath := filepath.Join(tmpDirA, "symlink3")
+
+	if err = testCopyHelperFSym(t, symlinkPath, dstDir); err == nil {
+		t.Fatal("expected ErrDirNotExists error, but got nil instead")
+	}
+	if err != ErrDirNotExists {
+		t.Fatalf("expected ErrDirNotExists error, but got %T: %s", err, err)
+	}
+
 }
 
 // C. SRC specifies a file and DST exists as a file. This should overwrite
@@ -341,6 +378,44 @@ func TestCopyCaseC(t *testing.T) {
 	}
 }
 
+// C. Symbol link following version:
+//    SRC specifies a file and DST exists as a file. This should overwrite
+//    the file at DST with the contents of the source file.
+func TestCopyCaseCFSym(t *testing.T) {
+	tmpDirA, tmpDirB := getTestTempDirs(t)
+	defer removeAllPaths(tmpDirA, tmpDirB)
+
+	// Load A and B with some sample files and directories.
+	createSampleDir(t, tmpDirA)
+	createSampleDir(t, tmpDirB)
+
+	symlinkPathBad := filepath.Join(tmpDirA, "symlink1")
+	symlinkPath := filepath.Join(tmpDirA, "symlink3")
+	linkTarget := filepath.Join(tmpDirA, "file1")
+	dstPath := filepath.Join(tmpDirB, "file2")
+
+	var err error
+
+	// first to test broken link
+	if err = testCopyHelperFSym(t, symlinkPathBad, dstPath); err == nil {
+		t.Fatalf("unexpected error %T: %s", err, err)
+	}
+
+	// test symbol link -> symbol link -> target
+	// Ensure they start out different.
+	if err = fileContentsEqual(t, linkTarget, dstPath); err == nil {
+		t.Fatal("expected different file contents")
+	}
+
+	if err = testCopyHelperFSym(t, symlinkPath, dstPath); err != nil {
+		t.Fatalf("unexpected error %T: %s", err, err)
+	}
+
+	if err = fileContentsEqual(t, linkTarget, dstPath); err != nil {
+		t.Fatal(err)
+	}
+}
+
 // D. SRC specifies a file and DST exists as a directory. This should place
 //    a copy of the source file inside it using the basename from SRC. Ensure
 //    this works whether DST has a trailing path separator or not.
@@ -392,6 +467,59 @@ func TestCopyCaseD(t *testing.T) {
 	}
 }
 
+// D. Symbol link following version:
+//    SRC specifies a file and DST exists as a directory. This should place
+//    a copy of the source file inside it using the basename from SRC. Ensure
+//    this works whether DST has a trailing path separator or not.
+func TestCopyCaseDFSym(t *testing.T) {
+	tmpDirA, tmpDirB := getTestTempDirs(t)
+	defer removeAllPaths(tmpDirA, tmpDirB)
+
+	// Load A and B with some sample files and directories.
+	createSampleDir(t, tmpDirA)
+	createSampleDir(t, tmpDirB)
+
+	srcPath := filepath.Join(tmpDirA, "symlink4")
+	linkTarget := filepath.Join(tmpDirA, "file1")
+	dstDir := filepath.Join(tmpDirB, "dir1")
+	dstPath := filepath.Join(dstDir, "symlink4")
+
+	var err error
+
+	// Ensure that dstPath doesn't exist.
+	if _, err = os.Stat(dstPath); !os.IsNotExist(err) {
+		t.Fatalf("did not expect dstPath %q to exist", dstPath)
+	}
+
+	if err = testCopyHelperFSym(t, srcPath, dstDir); err != nil {
+		t.Fatalf("unexpected error %T: %s", err, err)
+	}
+
+	if err = fileContentsEqual(t, linkTarget, dstPath); err != nil {
+		t.Fatal(err)
+	}
+
+	// Now try again but using a trailing path separator for dstDir.
+
+	if err = os.RemoveAll(dstDir); err != nil {
+		t.Fatalf("unable to remove dstDir: %s", err)
+	}
+
+	if err = os.MkdirAll(dstDir, os.FileMode(0755)); err != nil {
+		t.Fatalf("unable to make dstDir: %s", err)
+	}
+
+	dstDir = joinTrailingSep(tmpDirB, "dir1")
+
+	if err = testCopyHelperFSym(t, srcPath, dstDir); err != nil {
+		t.Fatalf("unexpected error %T: %s", err, err)
+	}
+
+	if err = fileContentsEqual(t, linkTarget, dstPath); err != nil {
+		t.Fatal(err)
+	}
+}
+
 // E. SRC specifies a directory and DST does not exist. This should create a
 //    directory at DST and copy the contents of the SRC directory into the DST
 //    directory. Ensure this works whether DST has a trailing path separator or
@@ -436,6 +564,52 @@ func TestCopyCaseE(t *testing.T) {
 	}
 }
 
+// E. Symbol link following version:
+//    SRC specifies a directory and DST does not exist. This should create a
+//    directory at DST and copy the contents of the SRC directory into the DST
+//    directory. Ensure this works whether DST has a trailing path separator or
+//    not.
+func TestCopyCaseEFSym(t *testing.T) {
+	tmpDirA, tmpDirB := getTestTempDirs(t)
+	defer removeAllPaths(tmpDirA, tmpDirB)
+
+	// Load A with some sample files and directories.
+	createSampleDir(t, tmpDirA)
+
+	srcDir := filepath.Join(tmpDirA, "dirSymlink")
+	linkTarget := filepath.Join(tmpDirA, "dir1")
+	dstDir := filepath.Join(tmpDirB, "testDir")
+
+	var err error
+
+	if err = testCopyHelperFSym(t, srcDir, dstDir); err != nil {
+		t.Fatalf("unexpected error %T: %s", err, err)
+	}
+
+	if err = dirContentsEqual(t, dstDir, linkTarget); err != nil {
+		t.Log("dir contents not equal")
+		logDirContents(t, tmpDirA)
+		logDirContents(t, tmpDirB)
+		t.Fatal(err)
+	}
+
+	// Now try again but using a trailing path separator for dstDir.
+
+	if err = os.RemoveAll(dstDir); err != nil {
+		t.Fatalf("unable to remove dstDir: %s", err)
+	}
+
+	dstDir = joinTrailingSep(tmpDirB, "testDir")
+
+	if err = testCopyHelperFSym(t, srcDir, dstDir); err != nil {
+		t.Fatalf("unexpected error %T: %s", err, err)
+	}
+
+	if err = dirContentsEqual(t, dstDir, linkTarget); err != nil {
+		t.Fatal(err)
+	}
+}
+
 // F. SRC specifies a directory and DST exists as a file. This should cause an
 //    error as it is not possible to overwrite a file with a directory.
 func TestCopyCaseF(t *testing.T) {
@@ -447,6 +621,7 @@ func TestCopyCaseF(t *testing.T) {
 	createSampleDir(t, tmpDirB)
 
 	srcDir := filepath.Join(tmpDirA, "dir1")
+	symSrcDir := filepath.Join(tmpDirA, "dirSymlink")
 	dstFile := filepath.Join(tmpDirB, "file1")
 
 	var err error
@@ -458,6 +633,15 @@ func TestCopyCaseF(t *testing.T) {
 	if err != ErrCannotCopyDir {
 		t.Fatalf("expected ErrCannotCopyDir error, but got %T: %s", err, err)
 	}
+
+	// now test with symbol link
+	if err = testCopyHelperFSym(t, symSrcDir, dstFile); err == nil {
+		t.Fatal("expected ErrCannotCopyDir error, but got nil instead")
+	}
+
+	if err != ErrCannotCopyDir {
+		t.Fatalf("expected ErrCannotCopyDir error, but got %T: %s", err, err)
+	}
 }
 
 // G. SRC specifies a directory and DST exists as a directory. This should copy
@@ -506,6 +690,54 @@ func TestCopyCaseG(t *testing.T) {
 	}
 }
 
+// G. Symbol link version:
+//    SRC specifies a directory and DST exists as a directory. This should copy
+//    the SRC directory and all its contents to the DST directory. Ensure this
+//    works whether DST has a trailing path separator or not.
+func TestCopyCaseGFSym(t *testing.T) {
+	tmpDirA, tmpDirB := getTestTempDirs(t)
+	defer removeAllPaths(tmpDirA, tmpDirB)
+
+	// Load A and B with some sample files and directories.
+	createSampleDir(t, tmpDirA)
+	createSampleDir(t, tmpDirB)
+
+	srcDir := filepath.Join(tmpDirA, "dirSymlink")
+	linkTarget := filepath.Join(tmpDirA, "dir1")
+	dstDir := filepath.Join(tmpDirB, "dir2")
+	resultDir := filepath.Join(dstDir, "dirSymlink")
+
+	var err error
+
+	if err = testCopyHelperFSym(t, srcDir, dstDir); err != nil {
+		t.Fatalf("unexpected error %T: %s", err, err)
+	}
+
+	if err = dirContentsEqual(t, resultDir, linkTarget); err != nil {
+		t.Fatal(err)
+	}
+
+	// Now try again but using a trailing path separator for dstDir.
+
+	if err = os.RemoveAll(dstDir); err != nil {
+		t.Fatalf("unable to remove dstDir: %s", err)
+	}
+
+	if err = os.MkdirAll(dstDir, os.FileMode(0755)); err != nil {
+		t.Fatalf("unable to make dstDir: %s", err)
+	}
+
+	dstDir = joinTrailingSep(tmpDirB, "dir2")
+
+	if err = testCopyHelperFSym(t, srcDir, dstDir); err != nil {
+		t.Fatalf("unexpected error %T: %s", err, err)
+	}
+
+	if err = dirContentsEqual(t, resultDir, linkTarget); err != nil {
+		t.Fatal(err)
+	}
+}
+
 // H. SRC specifies a directory's contents only and DST does not exist. This
 //    should create a directory at DST and copy the contents of the SRC
 //    directory (but not the directory itself) into the DST directory. Ensure
@@ -553,6 +785,55 @@ func TestCopyCaseH(t *testing.T) {
 	}
 }
 
+// H. Symbol link following version:
+//    SRC specifies a directory's contents only and DST does not exist. This
+//    should create a directory at DST and copy the contents of the SRC
+//    directory (but not the directory itself) into the DST directory. Ensure
+//    this works whether DST has a trailing path separator or not.
+func TestCopyCaseHFSym(t *testing.T) {
+	tmpDirA, tmpDirB := getTestTempDirs(t)
+	defer removeAllPaths(tmpDirA, tmpDirB)
+
+	// Load A with some sample files and directories.
+	createSampleDir(t, tmpDirA)
+
+	srcDir := joinTrailingSep(tmpDirA, "dirSymlink") + "."
+	linkTarget := filepath.Join(tmpDirA, "dir1")
+	dstDir := filepath.Join(tmpDirB, "testDir")
+
+	var err error
+
+	if err = testCopyHelperFSym(t, srcDir, dstDir); err != nil {
+		t.Fatalf("unexpected error %T: %s", err, err)
+	}
+
+	if err = dirContentsEqual(t, dstDir, linkTarget); err != nil {
+		t.Log("dir contents not equal")
+		logDirContents(t, tmpDirA)
+		logDirContents(t, tmpDirB)
+		t.Fatal(err)
+	}
+
+	// Now try again but using a trailing path separator for dstDir.
+
+	if err = os.RemoveAll(dstDir); err != nil {
+		t.Fatalf("unable to remove dstDir: %s", err)
+	}
+
+	dstDir = joinTrailingSep(tmpDirB, "testDir")
+
+	if err = testCopyHelperFSym(t, srcDir, dstDir); err != nil {
+		t.Fatalf("unexpected error %T: %s", err, err)
+	}
+
+	if err = dirContentsEqual(t, dstDir, linkTarget); err != nil {
+		t.Log("dir contents not equal")
+		logDirContents(t, tmpDirA)
+		logDirContents(t, tmpDirB)
+		t.Fatal(err)
+	}
+}
+
 // I. SRC specifies a directory's contents only and DST exists as a file. This
 //    should cause an error as it is not possible to overwrite a file with a
 //    directory.
@@ -565,6 +846,7 @@ func TestCopyCaseI(t *testing.T) {
 	createSampleDir(t, tmpDirB)
 
 	srcDir := joinTrailingSep(tmpDirA, "dir1") + "."
+	symSrcDir := filepath.Join(tmpDirB, "dirSymlink")
 	dstFile := filepath.Join(tmpDirB, "file1")
 
 	var err error
@@ -576,6 +858,15 @@ func TestCopyCaseI(t *testing.T) {
 	if err != ErrCannotCopyDir {
 		t.Fatalf("expected ErrCannotCopyDir error, but got %T: %s", err, err)
 	}
+
+	// now try with symbol link of dir
+	if err = testCopyHelperFSym(t, symSrcDir, dstFile); err == nil {
+		t.Fatal("expected ErrCannotCopyDir error, but got nil instead")
+	}
+
+	if err != ErrCannotCopyDir {
+		t.Fatalf("expected ErrCannotCopyDir error, but got %T: %s", err, err)
+	}
 }
 
 // J. SRC specifies a directory's contents only and DST exists as a directory.
@@ -595,6 +886,11 @@ func TestCopyCaseJ(t *testing.T) {
 
 	var err error
 
+	// first to create an empty dir
+	if err = os.MkdirAll(dstDir, os.FileMode(0755)); err != nil {
+		t.Fatalf("unable to make dstDir: %s", err)
+	}
+
 	if err = testCopyHelper(t, srcDir, dstDir); err != nil {
 		t.Fatalf("unexpected error %T: %s", err, err)
 	}
@@ -623,3 +919,56 @@ func TestCopyCaseJ(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+// J. Symbol link following version:
+//    SRC specifies a directory's contents only and DST exists as a directory.
+//    This should copy the contents of the SRC directory (but not the directory
+//    itself) into the DST directory. Ensure this works whether DST has a
+//    trailing path separator or not.
+func TestCopyCaseJFSym(t *testing.T) {
+	tmpDirA, tmpDirB := getTestTempDirs(t)
+	defer removeAllPaths(tmpDirA, tmpDirB)
+
+	// Load A and B with some sample files and directories.
+	createSampleDir(t, tmpDirA)
+	createSampleDir(t, tmpDirB)
+
+	srcDir := joinTrailingSep(tmpDirA, "dirSymlink") + "."
+	linkTarget := filepath.Join(tmpDirA, "dir1")
+	dstDir := filepath.Join(tmpDirB, "dir5")
+
+	var err error
+
+	// first to create an empty dir
+	if err = os.MkdirAll(dstDir, os.FileMode(0755)); err != nil {
+		t.Fatalf("unable to make dstDir: %s", err)
+	}
+
+	if err = testCopyHelperFSym(t, srcDir, dstDir); err != nil {
+		t.Fatalf("unexpected error %T: %s", err, err)
+	}
+
+	if err = dirContentsEqual(t, dstDir, linkTarget); err != nil {
+		t.Fatal(err)
+	}
+
+	// Now try again but using a trailing path separator for dstDir.
+
+	if err = os.RemoveAll(dstDir); err != nil {
+		t.Fatalf("unable to remove dstDir: %s", err)
+	}
+
+	if err = os.MkdirAll(dstDir, os.FileMode(0755)); err != nil {
+		t.Fatalf("unable to make dstDir: %s", err)
+	}
+
+	dstDir = joinTrailingSep(tmpDirB, "dir5")
+
+	if err = testCopyHelperFSym(t, srcDir, dstDir); err != nil {
+		t.Fatalf("unexpected error %T: %s", err, err)
+	}
+
+	if err = dirContentsEqual(t, dstDir, linkTarget); err != nil {
+		t.Fatal(err)
+	}
+}