Add migration support for TOML config changes

This patch allows running `alacritty migrate` to automatically apply
configuration changes made to the TOML format, like moving `ipc_socket`
to `general.ipc_socket`.

This should reduce the friction of moving around individual options
significantly, while also persisting the format of the existing TOML
file thanks to `toml_edit`.

The YAML migration has been simplified significantly to only switch the
format of the file from YAML to TOML. The new TOML features are used for
everything else.

2 files changed, 10 insertions, 10 deletions

diff --git a/alacritty_config_derive/src/config_deserialize/de_struct.rs b/alacritty_config_derive/src/config_deserialize/de_struct.rs
index d2a7dd82..ad38863e 100644
--- a/alacritty_config_derive/src/config_deserialize/de_struct.rs
+++ b/alacritty_config_derive/src/config_deserialize/de_struct.rs
@@ -155,6 +155,7 @@ fn field_deserializer(field_streams: &mut FieldStreams, field: &Field) -> Result
                 if let Some(warning) = parsed.param {
                     message = format!("{}; {}", message, warning.value());
                 }
+                message.push_str("\nUse `alacritty migrate` to automatically resolve it");
 
                 // Append stream to log deprecation/removal warning.
                 match_assignment_stream.extend(quote! {
diff --git a/alacritty_config_derive/tests/config.rs b/alacritty_config_derive/tests/config.rs
index 27a968ed..be140cbe 100644
--- a/alacritty_config_derive/tests/config.rs
+++ b/alacritty_config_derive/tests/config.rs
@@ -1,4 +1,4 @@
-use std::sync::{Arc, Mutex};
+use std::sync::{Arc, Mutex, OnceLock};
 
 use log::{Level, Log, Metadata, Record};
 use serde::Deserialize;
@@ -83,10 +83,8 @@ struct NewType(usize);
 
 #[test]
 fn config_deserialize() {
-    let logger = unsafe {
-        LOGGER = Some(Logger::default());
-        LOGGER.as_mut().unwrap()
-    };
+    static LOGGER: OnceLock<Logger> = OnceLock::new();
+    let logger = LOGGER.get_or_init(Logger::default);
 
     log::set_logger(logger).unwrap();
     log::set_max_level(log::LevelFilter::Warn);
@@ -134,15 +132,16 @@ fn config_deserialize() {
     ]);
     let warn_logs = logger.warn_logs.lock().unwrap();
     assert_eq!(warn_logs.as_slice(), [
-        "Config warning: field1 has been deprecated; use field2 instead",
-        "Config warning: enom_error has been deprecated",
-        "Config warning: gone has been removed; it's gone",
+        "Config warning: field1 has been deprecated; use field2 instead\nUse `alacritty migrate` \
+         to automatically resolve it",
+        "Config warning: enom_error has been deprecated\nUse `alacritty migrate` to automatically \
+         resolve it",
+        "Config warning: gone has been removed; it's gone\nUse `alacritty migrate` to \
+         automatically resolve it",
         "Unused config key: field3",
     ]);
 }
 
-static mut LOGGER: Option<Logger> = None;
-
 /// Logger storing all messages for later validation.
 #[derive(Default)]
 struct Logger {