Ci build update (#1151)

update ci build images, remove ubuntu 20.04 and update a few others, fix some newer clang-tidy warnings

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

include/CLI/App.hpp

@@ -46,7 +46,15 @@ namespace CLI {
 #endif
 
 namespace detail {
-enum class Classifier { NONE, POSITIONAL_MARK, SHORT, LONG, WINDOWS_STYLE, SUBCOMMAND, SUBCOMMAND_TERMINATOR };
+enum class Classifier : std::uint8_t {
+    NONE,
+    POSITIONAL_MARK,
+    SHORT,
+    LONG,
+    WINDOWS_STYLE,
+    SUBCOMMAND,
+    SUBCOMMAND_TERMINATOR
+};
 struct AppFriend;
 }  // namespace detail
 
@@ -60,7 +68,7 @@ CLI11_INLINE std::string help(const App *app, const Error &e);
 
 /// enumeration of modes of how to deal with extras in config files
 
-enum class config_extras_mode : char { error = 0, ignore, ignore_all, capture };
+enum class config_extras_mode : std::uint8_t { error = 0, ignore, ignore_all, capture };
 
 class App;
 
@@ -242,7 +250,7 @@ class App {
     /// specify that positional arguments come at the end of the argument sequence not inheritable
     bool positionals_at_end_{false};
 
-    enum class startup_mode : char { stable, enabled, disabled };
+    enum class startup_mode : std::uint8_t { stable, enabled, disabled };
     /// specify the startup mode for the app
     /// stable=no change, enabled= startup enabled, disabled=startup disabled
     startup_mode default_startup{startup_mode::stable};

include/CLI/Error.hpp

@@ -41,7 +41,7 @@ namespace CLI {
 
 /// These codes are part of every error in CLI. They can be obtained from e using e.exit_code or as a quick shortcut,
 /// int values from e.get_error_code().
-enum class ExitCodes {
+enum class ExitCodes : int {
     Success = 0,
     IncorrectConstruction = 100,
     BadNameString,

include/CLI/FormatterFwd.hpp

@@ -29,7 +29,7 @@ class App;
 /// This is passed in by App; all user classes must accept this as
 /// the second argument.
 
-enum class AppFormatMode {
+enum class AppFormatMode : std::uint8_t {
     Normal,  ///< The normal, detailed help
     All,     ///< A fully expanded help
     Sub,     ///< Used when printed as part of expanded subcommand

include/CLI/TypeTools.hpp

@@ -33,7 +33,7 @@ namespace CLI {
 namespace detail {
 // Based generally on https://rmf.io/cxx11/almost-static-if
 /// Simple empty scoped class
-enum class enabler {};
+enum class enabler : std::uint8_t {};
 
 /// An instance to use in EnableIf
 constexpr enabler dummy = {};
@@ -628,7 +628,7 @@ struct expected_count<T, typename std::enable_if<!is_mutable_container<T>::value
 };
 
 // Enumeration of the different supported categorizations of objects
-enum class object_category : int {
+enum class object_category : std::uint8_t {
     char_value = 1,
     integral_value = 2,
     unsigned_integral = 4,

include/CLI/Validators.hpp

@@ -185,7 +185,7 @@ class CustomValidator : public Validator {
 namespace detail {
 
 /// CLI enumeration of different file types
-enum class path_type { nonexistent, file, directory };
+enum class path_type : std::uint8_t { nonexistent, file, directory };
 
 /// get the type of the path from a file name
 CLI11_INLINE path_type check_path(const char *file) noexcept;
@@ -356,6 +356,7 @@ template <
     typename T,
     enable_if_t<!is_copyable_ptr<typename std::remove_reference<T>::type>::value, detail::enabler> = detail::dummy>
 typename std::remove_reference<T>::type &smart_deref(T &value) {
+    // NOLINTNEXTLINE
     return value;
 }
 /// Generate a string representation of a set
@@ -721,7 +722,7 @@ class AsNumberWithUnit : public Validator {
     /// CASE_SENSITIVE/CASE_INSENSITIVE controls how units are matched.
     /// UNIT_OPTIONAL/UNIT_REQUIRED throws ValidationError
     ///   if UNIT_REQUIRED is set and unit literal is not found.
-    enum Options {
+    enum Options : std::uint8_t {
         CASE_SENSITIVE = 0,
         CASE_INSENSITIVE = 1,
         UNIT_OPTIONAL = 0,

include/CLI/impl/Formatter_inl.hpp

@@ -291,11 +291,11 @@ CLI11_INLINE std::string Formatter::make_option(const Option *opt, bool is_posit
         int shortNamesOverSize = 0;
 
         // Print short names
-        if(shortNames.length() > 0) {
+        if(!shortNames.empty()) {
             shortNames = "  " + shortNames;  // Indent
-            if(longNames.length() == 0 && opts.length() > 0)
+            if(longNames.empty() && !opts.empty())
                 shortNames += opts;  // Add opts if only short names and no long names
-            if(longNames.length() > 0)
+            if(!longNames.empty())
                 shortNames += ",";
             if(static_cast<int>(shortNames.length()) >= shortNamesColumnWidth) {
                 shortNames += " ";
@@ -312,8 +312,8 @@ CLI11_INLINE std::string Formatter::make_option(const Option *opt, bool is_posit
         const auto adjustedLongNamesColumnWidth = longNamesColumnWidth - shortNamesOverSize;
 
         // Print long names
-        if(longNames.length() > 0) {
-            if(opts.length() > 0)
+        if(!longNames.empty()) {
+            if(!opts.empty())
                 longNames += opts;
             if(static_cast<int>(longNames.length()) >= adjustedLongNamesColumnWidth)
                 longNames += " ";

include/CLI/impl/Split_inl.hpp

@@ -109,7 +109,7 @@ get_names(const std::vector<std::string> &input, bool allow_non_standard) {
     std::vector<std::string> long_names;
     std::string pos_name;
     for(std::string name : input) {
-        if(name.length() == 0) {
+        if(name.empty()) {
             continue;
         }
         if(name.length() > 1 && name[0] == '-' && name[1] != '-') {