Add configured_unstable_options field on Config Struct

This new internal Vec is used to track all unstable options specified
when running on the stable channel.

Author: ytmimi

src/config/config_type.rs

@@ -64,6 +64,8 @@ macro_rules! create_config {
             // if a license_template_path has been specified, successfully read, parsed and compiled
             // into a regex, it will be stored here
             pub license_template: Option<Regex>,
+            // Unstable Options specified on the stable channel
+            configured_unstable_options: Option<Vec<String>>,
             // For each config item, we store a bool indicating whether it has
             // been accessed and the value, and a bool whether the option was
             // manually initialised, or taken from the default,
@@ -146,6 +148,7 @@ macro_rules! create_config {
             }
 
             fn fill_from_parsed_config(mut self, parsed: PartialConfig, dir: &Path) -> Config {
+                let mut unstable_options = vec![];
             $(
                 if let Some(val) = parsed.$i {
                     if self.$i.3 {
@@ -158,10 +161,21 @@ macro_rules! create_config {
                         } else {
                             eprintln!("Warning: can't set `{} = {:?}`, unstable features are only \
                                        available in nightly channel.", stringify!($i), val);
+                            // only set abort_on_unrecognised_options, and store all other
+                            // nightly only options
+                            if stringify!($i) != "abort_on_unrecognised_options" {
+                                unstable_options.push(format!("{} = {:?}", stringify!($i), val));
+                            } else {
+                                self.$i.1 = true;
+                                self.$i.2 = val;
+                            }
                         }
                     }
                 }
             )+
+                if unstable_options.len() > 0 {
+                    self.configured_unstable_options = Some(unstable_options);
+                }
                 self.set_heuristics();
                 self.set_license_template();
                 self.set_ignore(dir);
@@ -438,6 +452,7 @@ macro_rules! create_config {
             fn default() -> Config {
                 Config {
                     license_template: None,
+                    configured_unstable_options: None,
                     $(
                         $i: (Cell::new(false), false, $def, $stb),
                     )+