fix: align sentence-case implementation

Author: hasghari

@commitlint/cz-commitlint/src/utils/case-fn.test.ts

@@ -64,10 +64,16 @@ test('should convert text correctly', () => {
 	expect(rule('TEST_FOOBar-baz baz')).toBe('TEST_FOOBAR-BAZ BAZ');
 
 	rule = getCaseFn([RuleConfigSeverity.Warning, 'always', 'sentence-case']);
-	expect(rule('TEST_FOOBar-baz baz')).toBe('Test_foobar-baz baz');
+	expect(rule('TEST_FOOBar-baz baz')).toBe('TEST_FOOBar-baz baz');
 
 	rule = getCaseFn([RuleConfigSeverity.Warning, 'always', 'sentencecase']);
-	expect(rule('TEST_FOOBar-baz baz')).toBe('Test_foobar-baz baz');
+	expect(rule('TEST_FOOBar-baz baz')).toBe('TEST_FOOBar-baz baz');
+
+	rule = getCaseFn([RuleConfigSeverity.Warning, 'always', 'sentence-case']);
+	expect(rule('update API')).toBe('Update API');
+
+	rule = getCaseFn([RuleConfigSeverity.Warning, 'always', 'sentencecase']);
+	expect(rule('update API')).toBe('Update API');
 
 	rule = getCaseFn([RuleConfigSeverity.Warning, 'always', 'lower-case']);
 	expect(rule('TEST_FOOBar-baz baz')).toBe('test_foobar-baz baz');

@commitlint/cz-commitlint/src/utils/case-fn.ts

@@ -42,8 +42,7 @@ export default function getCaseFn(rule?: Rule): CaseFn {
 			return (input: string) => input.toUpperCase();
 		case 'sentence-case':
 		case 'sentencecase':
-			return (input: string) =>
-				`${input.charAt(0).toUpperCase()}${input.substring(1).toLowerCase()}`;
+			return (input: string) => upperFirst(input);
 		case 'lower-case':
 		case 'lowercase':
 		case 'lowerCase': // Backwards compat config-angular v4

@commitlint/ensure/src/case.ts

@@ -43,7 +43,7 @@ function toCase(input: string, target: TargetCaseType): string {
 			return input.toUpperCase();
 		case 'sentence-case':
 		case 'sentencecase':
-			return input.charAt(0).toUpperCase() + input.slice(1);
+			return upperFirst(input);
 		case 'lower-case':
 		case 'lowercase':
 		case 'lowerCase': // Backwards compat config-angular v4