Fix relative symlinks copying

All relative paths of symbolic links should be resolved from the
directory where the link is located. The current working directory
does not affect the resolution of the path. A symbolic link can
be absolute or relative, and may or may not have a leading dot.
Directory content example:
file
symlink -> file
Copying of the directory with such content does not work currently.
When copying `symlink`, `Copy` returns an error because the `file`
does not exist in the current working directory. In the existing
tests, there is a symbolic link named "symlink" that points to a
file named "README.md". However, when resolving the path of the
file, the file is located in the repository's root directory,
not the test case directory, and copying of these dirs work fine.

The solution is to check whether the resolved path is absolute
or not. If it is not, append it to the file's directory path.

all_test.go

@@ -26,7 +26,7 @@ func TestMain(m *testing.M) {
 
 func teardown(m *testing.M) {
 	os.RemoveAll("test/data/case03/case01")
-	os.RemoveAll("test/data/case03/relative_case01")
+	os.Remove("test/data/case03/relative_foo")
 	os.RemoveAll("test/data.copy")
 	os.RemoveAll("test/data.copyTime")
 	os.RemoveAll("test/owned-by-root") // Do not check the error ;)

copy.go

@@ -6,7 +6,6 @@ import (
 	"io/fs"
 	"os"
 	"path/filepath"
-	"strings"
 	"time"
 
 	"golang.org/x/sync/errgroup"
@@ -293,7 +292,7 @@ func onsymlink(src, dest string, opt Options) error {
 		if err != nil {
 			return err
 		}
-		if strings.HasPrefix(orig, ".") {
+		if !filepath.IsAbs(orig) {
 			// orig is a relative link: need to add src dir to orig
 			orig = filepath.Join(filepath.Dir(src), orig)
 		}

symlink_test.go

@@ -16,7 +16,7 @@ func TestOptions_OnSymlink(t *testing.T) {
 	info, err := os.Lstat("test/data.copy/case03.deep/case01")
 	Expect(t, err).ToBe(nil)
 	Expect(t, info.Mode()&os.ModeSymlink).ToBe(os.FileMode(0))
-	info, err = os.Lstat("test/data.copy/case03.deep/relative_case01")
+	info, err = os.Lstat("test/data.copy/case03.deep/relative_foo")
 	Expect(t, err).ToBe(nil)
 	Expect(t, info.Mode()&os.ModeSymlink).ToBe(os.FileMode(0))
 
@@ -26,12 +26,17 @@ func TestOptions_OnSymlink(t *testing.T) {
 	info, err = os.Lstat("test/data.copy/case03.shallow/case01")
 	Expect(t, err).ToBe(nil)
 	Expect(t, info.Mode()&os.ModeSymlink).Not().ToBe(os.FileMode(0))
+	linkTarget, err := os.Readlink("test/data.copy/case03.shallow/relative_foo")
+	Expect(t, err).ToBe(nil)
+	Expect(t, linkTarget).ToBe("foo")
 
 	opt = Options{OnSymlink: func(string) SymlinkAction { return Skip }}
 	err = Copy("test/data/case03", "test/data.copy/case03.skip", opt)
 	Expect(t, err).ToBe(nil)
 	_, err = os.Stat("test/data.copy/case03.skip/case01")
 	Expect(t, os.IsNotExist(err)).ToBe(true)
+	_, err = os.Stat("test/data.copy/case03.skip/relative_foo")
+	Expect(t, os.IsNotExist(err)).ToBe(true)
 
 	err = Copy("test/data/case03", "test/data.copy/case03.default")
 	Expect(t, err).ToBe(nil)

test_setup_test.go

@@ -11,8 +11,8 @@ import (
 func setup(m *testing.M) {
 	os.RemoveAll("test/data.copy")
 	os.MkdirAll("test/data.copy", os.ModePerm)
-	os.Symlink("test/data/case01", "test/data/case03/case01")
-	os.Symlink("../case01", "test/data/case03/relative_case01")
+	os.Symlink("../case01", "test/data/case03/case01")
+	os.Symlink("foo", "test/data/case03/relative_foo")
 	os.Chmod("test/data/case07/dir_0555", 0o555)
 	os.Chmod("test/data/case07/file_0444", 0o444)
 	syscall.Mkfifo("test/data/case11/foo/bar", 0o555)

test_setup_x_test.go

@@ -10,7 +10,7 @@ import (
 func setup(m *testing.M) {
 	os.RemoveAll("test/data.copy")
 	os.MkdirAll("test/data.copy", os.ModePerm)
-	os.Symlink("test/data/case01", "test/data/case03/case01")
+	os.Symlink("../case01", "test/data/case03/case01")
 	os.Chmod("test/data/case07/dir_0555", 0555)
 	os.Chmod("test/data/case07/file_0444", 0444)
 }