os: add function to expand "~" to home directory (#11362)

vlib/os/os.v

@@ -336,6 +336,19 @@ pub fn home_dir() string {
 	}
 }
 
+// expand_tilde_to_home expands the character `~` in `path` to the user's home directory.
+// See also `home_dir()`.
+pub fn expand_tilde_to_home(path string) string {
+	if path == '~' {
+		return home_dir().trim_right(path_separator)
+	}
+	if path.starts_with('~' + path_separator) {
+		return path.replace_once('~' + path_separator, home_dir().trim_right(path_separator) +
+			path_separator)
+	}
+	return path
+}
+
 // write_file writes `text` data to a file in `path`.
 pub fn write_file(path string, text string) ? {
 	mut f := create(path) ?

vlib/os/os_test.v

@@ -750,3 +750,11 @@ fn test_utime() {
 	os.utime(filename, int(atime), int(mtime)) or { panic(err) }
 	assert os.file_last_mod_unix(filename) == mtime
 }
+
+fn test_expand_tilde_to_home() {
+	home_test := os.join_path(os.home_dir(), 'test', 'tilde', 'expansion')
+	home_expansion_test := os.expand_tilde_to_home(os.join_path('~', 'test', 'tilde',
+		'expansion'))
+	assert home_test == home_expansion_test
+	assert os.expand_tilde_to_home('~') == os.home_dir()
+}