os: cp_r fn to copy files recursively

vlib/os/os.v

@@ -151,7 +151,40 @@ pub fn cp(old, new string) ?bool {
 	}
 }
 
-fn vfopen(path, mode string) voidptr { //*C.FILE {
+pub fn cp_r(source_path, dest_path string, overwrite bool) ?bool{
+	if !os.file_exists(source_path) {
+		return error('Source path doesn\'t exist')
+	}
+	//single file copy
+	if !os.is_dir(source_path) {
+		adjasted_path := if os.is_dir(dest_path) { 
+			filepath.join(dest_path, os.basedir(source_path)) } else { dest_path }
+		if os.file_exists(adjasted_path) {
+			if overwrite { os.rm(adjasted_path) }
+			else { return error('Destination file path already exist') }
+		}
+		os.cp(source_path, adjasted_path) or { return error(err) }
+		return true
+	}
+	if !os.is_dir(dest_path) {
+		return error('Destination path is not a valid directory')
+	}
+	files := os.ls(source_path) or { return error(err) }
+	for file in files {
+		sp := filepath.join(source_path, file)
+		dp := filepath.join(dest_path, file)
+		if os.is_dir(sp) {
+			os.mkdir(dp)
+		}
+		cp_r(sp, dp, overwrite) or {
+			os.rmdir(dp)
+			panic(err) 
+		}
+	}
+	return true
+}
+
+fn vfopen(path, mode string) *C.FILE {
 	$if windows {
 		return C._wfopen(path.to_wide(), mode.to_wide())
 	} $else {

vlib/os/os_test.v

@@ -130,6 +130,24 @@ fn test_cp() {
   }
 }
 
+fn test_cp_r() {
+  //fileX -> dir/fileX
+  os.write_file('ex1.txt', 'wow!')
+  os.mkdir('ex')
+  os.cp_r('ex1.txt', 'ex', false) or { panic(err) }
+  old := os.read_file('ex1.txt') or { panic(err) }
+  new := os.read_file('ex/ex1.txt') or { panic(err) }
+  assert old == new
+  os.mkdir('ex/ex2')
+  os.write_file('ex2.txt', 'great!')
+  os.cp_r('ex2.txt', 'ex/ex2', false) or { panic(err) }
+  old2 := os.read_file('ex2.txt') or { panic(err) }
+  new2 := os.read_file('ex/ex2/ex2.txt') or { panic(err) }
+  assert old2 == new2
+  //recurring on dir -> local dir
+  os.cp_r('ex', './', true) or { panic(err) }
+}
+
 //fn test_fork() {
 //  pid := os.fork()
 //  if pid == 0 {