fix: recognize BREAKING-CHANGE trailers (#40)

> 16. `BREAKING-CHANGE` MUST be synonymous with `BREAKING CHANGE`, when used as a token in a footer.
> -- https://www.conventionalcommits.org/en/v1.0.0/#specification

Fixes #39

corpus/body.txt

@@ -163,11 +163,14 @@ BREAKING CHANGE
 test
 
 BREAKING CHANGE: My message
-
+BREAKING-CHANGE: also valid
 --------------------------------------------------------------------------------
 
 (source
   (message
+    (breaking_change
+      (token)
+      (value))
     (breaking_change
       (token)
       (value))))

grammar.js

@@ -13,6 +13,7 @@ const COMMENT_TITLE = /[^\n\r:\uff1a]+[:\uff1a]\s*\r?\n/;
 const TRAILER_TOKEN = /[a-zA-Z-]+[ ]*[:\uff1a] /;
 const GENERATED_COMMENT_TITLE = /[^\n\r:\uff1a]+[:\uff1a][ ]*/;
 const NUMBER = /\d+/;
+const BREAKING_CHANGE = /BREAKING[- ]CHANGE/;
 
 module.exports = grammar({
   name: 'gitcommit',
@@ -56,7 +57,12 @@ module.exports = grammar({
       seq(alias(TRAILER_TOKEN, $.token), alias(ANYTHING, $.value)),
 
     breaking_change: ($) =>
-      seq(alias('BREAKING CHANGE', $.token), alias(ANYTHING, $.value)),
+      seq(
+        // BREAKING_CHANGE conflicts with TRAILER_TOKEN, an so requires higher
+        // lexical precedence
+        alias(token(prec(1, BREAKING_CHANGE)), $.token),
+        alias(ANYTHING, $.value)
+      ),
 
     comment: ($) =>
       seq(

src/grammar.json

@@ -287,8 +287,15 @@
         {
           "type": "ALIAS",
           "content": {
-            "type": "STRING",
-            "value": "BREAKING CHANGE"
+            "type": "TOKEN",
+            "content": {
+              "type": "PREC",
+              "value": 1,
+              "content": {
+                "type": "PATTERN",
+                "value": "BREAKING[- ]CHANGE"
+              }
+            }
           },
           "named": true,
           "value": "token"