os: remove base_dir(); dir() and base() fixes

vlib/os/os.v

@@ -642,21 +642,46 @@ pub fn file_ext(path string) string {
 	return path[pos..]
 }
 
-// dir will return the part of `path` before the last occurence of a `path_separator`.
+// dir returns all but the last element of path, typically the path's directory.
+// After dropping the final element, trailing slashes are removed.
+// If the path is empty, dir returns ".". If the path consists entirely of separators,
+// dir returns a single separator.
+// The returned path does not end in a separator unless it is the root directory.
 pub fn dir(path string) string {
-	pos := path.last_index(path_separator) or {
+	if path == '' {
 		return '.'
 	}
+	mut pos := path.last_index(path_separator) or {
+		return '.'
+	}
+	if path.ends_with(path_separator) {
+		pos--
+	}
 	return path[..pos]
 }
 
-// base_dir will return the base directory of `path`.
-pub fn base_dir(path string) string {
-	posx := path.last_index(path_separator) or {
+// base returns the last element of path.
+// Trailing path separators are removed before extracting the last element.
+// If the path is empty, base returns ".". If the path consists entirely of separators, base returns a
+// single separator.
+pub fn base(path string) string {
+	if path == '' {
+		return '.'
+	}
+	if path == path_separator {
+		return path_separator
+	}
+	if path.ends_with(path_separator) {
+		path2 := path[..path.len-1]
+		pos := path2.last_index(path_separator) or {
+			return path2.clone()
+		}
+		return path2[pos+1..]
+	}
+	pos := path.last_index(path_separator) or {
 		return path.clone()
 	}
-	// NB: *without* terminating /
-	return path[..posx]
+	return path[pos+1..]
 }
 
 // file_name will return all characters found after the last occurence of `path_separator`.

vlib/os/os_test.v

@@ -446,13 +446,15 @@ fn test_dir() {
 	assert os.dir('os') == '.'
 }
 
-fn test_basedir() {
+fn test_base() {
 	$if windows {
-		assert os.base_dir('v\\vlib\\os') == 'v\\vlib'
+		assert os.base('v\\vlib\\os') == 'os'
+		assert os.base('v\\vlib\\os\\') == 'os'
 	} $else {
-		assert os.base_dir('v/vlib/os') == 'v/vlib'
+		assert os.base('v/vlib/os') == 'os'
+		assert os.base('v/vlib/os/') == 'os'
 	}
-	assert os.base_dir('filename') == 'filename'
+	assert os.base('filename') == 'filename'
 }
 
 fn test_uname() {