[Batch File] Fix empty comments exceeding to next line

This commit fixes "label comment" related patterns, to only scope leading
colons `punctuation.definition.comment`.

Label comments make use of invalid labels being ignored.
A label is invalid, if the first character after leading colon is a "metachar".

A label starting with `::` is already an invalid label and thus can be followed
by any (meta) char to still be a "valid" comment.

The wrong pattern was the real reason for the issue addressed by PR sublimehq#3992.

Batch File/Batch File.sublime-syntax

@@ -48,7 +48,7 @@ variables:
   eoc: (?=\s*{{eoc_char}})
   eoc_char: '[\n|&]'
 
-  label_comment: ':+[^{{label_start}}]'
+  label_comment: ':(?::+|(?!{{label_start}}))'
   label_start: '[^{{metachar}}:+]'
 
   path_terminator_chars: '[\s,;"{{redir_or_eoc_char}}]'

Batch File/tests/syntax_test_batch_file.bat

@@ -68,19 +68,19 @@ continuation
 :: ^^^^^^^^^^ comment.line.colon.dosbatch
 
    :+ Me too!
-:: ^^ punctuation.definition.comment.dosbatch
+:: ^ punctuation.definition.comment.dosbatch
 
    := Me too!
-:: ^^ punctuation.definition.comment.dosbatch
+:: ^ punctuation.definition.comment.dosbatch
 
    :, Me too!
-:: ^^ punctuation.definition.comment.dosbatch
+:: ^ punctuation.definition.comment.dosbatch
 
    :; Me too!
-:: ^^ punctuation.definition.comment.dosbatch
+:: ^ punctuation.definition.comment.dosbatch
 
    : Me too!
-:: ^^ punctuation.definition.comment.dosbatch
+:: ^ punctuation.definition.comment.dosbatch
 
    ::^
    Me too!
@@ -97,19 +97,19 @@ continuation
 
    :> ignored content ( & | )
 :: ^^^^^^^^^^^^^^^^^^^^^^^^^^^ comment.line.colon.dosbatch
-:: ^^ punctuation.definition.comment.dosbatch
+:: ^ punctuation.definition.comment.dosbatch
 
    :< ignored content ( & | )
 :: ^^^^^^^^^^^^^^^^^^^^^^^^^^^ comment.line.colon.dosbatch
-:: ^^ punctuation.definition.comment.dosbatch
+:: ^ punctuation.definition.comment.dosbatch
 
    :& ignored content ( & | )
 :: ^^^^^^^^^^^^^^^^^^^^^^^^^^^ comment.line.colon.dosbatch
-:: ^^ punctuation.definition.comment.dosbatch
+:: ^ punctuation.definition.comment.dosbatch
 
    :| ignored content ( & | )
 :: ^^^^^^^^^^^^^^^^^^^^^^^^^^^ comment.line.colon.dosbatch
-:: ^^ punctuation.definition.comment.dosbatch
+:: ^ punctuation.definition.comment.dosbatch
 
 ECHO &&:: A comment
 ::   ^^ keyword.operator.logical.dosbatch
@@ -139,6 +139,24 @@ ECHO : Not a comment ^
 :: <- - comment
 ::^^^^^^^^^^^^  - comment
 
+: empty comment line, followed by command
+:
+ECHO Not a comment
+:: <- - comment
+::^^^^^^^^^^^^^^^^ - comment
+
+:: empty comment line, followed by command
+::
+ECHO Not a comment
+:: <- - comment
+::^^^^^^^^^^^^^^^^ - comment
+
+::: empty comment line, followed by command
+:::
+ECHO Not a comment
+:: <- - comment
+::^^^^^^^^^^^^^^^^ - comment
+
 :::: [ @ Operator ] :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
 
    @