fix: add implicit (?-i) flags

See #727.

internal/check/definition.go

@@ -329,6 +329,15 @@ func updateExceptions(previous []string, current map[string]struct{}) (*regexp2.
 		return len(previous[p]) > len(previous[q])
 	})
 
+	// NOTE: We need to add `(?-i)` to each term that doesn't already have it,
+	// otherwise any instance of the `(?i)` flag will be set for the entire
+	// expression.
+	for i, term := range previous {
+		if !strings.HasPrefix(term, "(?i)") {
+			previous[i] = fmt.Sprintf("(?-i)%s", term)
+		}
+	}
+
 	regex := makeRegexp(
 		"",
 		false,

testdata/features/misc.feature

@@ -10,6 +10,7 @@ Feature: Misc
             test.md:17:11:Vale.Terms:Use 'Log4j' instead of 'log4j'.
             test.md:19:1:Vale.Terms:Use 'ABCDEF' instead of 'ABCDEf'.
             test.md:21:1:Vale.Terms:Use 'ABC-DEF' instead of 'ABC-DEf'.
+            test.md:23:1:Vale.Terms:Use 'PLuG' instead of 'plug'.
             """
 
     Scenario: Multiple Vocabs

testdata/fixtures/vocab/Basic/test.md

@@ -18,4 +18,8 @@ I use the log4j library.
 
 ABCDEf
 
-ABC-DEf
+ABC-DEf
+
+plug
+
+Github

testdata/fixtures/vocab/styles/Vocab/Basic/accept.txt

@@ -5,3 +5,5 @@ Documentarians
 Log4j
 ABCDEF
 ABC-DEF
+PLuG
+(?i)GitHub