[Batch File] Fix line continuation

This commit applies the following rule:

If `^` appears at the end of a line, the linefeed is stripped and the next
character is escaped or uses its special meaning, if any.
If the next character is also a linefeed, it is treated literal.

REM command seems to be working special by line continuation working only
directly after the first token.

Batch File/Batch File.sublime-syntax

@@ -1,6 +1,7 @@
 %YAML 1.2
 ---
 # https://www.sublimetext.com/docs/syntax.html
+# https://stackoverflow.com/questions/4094699/how-does-the-windows-command-interpreter-cmd-exe-parse-scripts/4095133#4095133
 name: Batch File
 scope: source.dosbatch
 version: 2
@@ -836,7 +837,19 @@ contexts:
     - include: cmd-arg-help
     - include: unquoted-eol-pop
     - match: (?=\S)
-      set: cmd-rem-comment-body
+      set:
+        - cmd-rem-comment-body
+        - cmd-rem-comment-begin
+
+  cmd-rem-comment-begin:
+    # In REM comments only the first continuation directly following
+    # the first token is taken into account.
+    - meta_include_prototype: false
+    - match: \^\n
+      scope: punctuation.separator.continuation.line.dosbatch
+      set: line-continuation-body
+    - match: (?={{metachar}})
+      pop: 1
 
   cmd-rem-comment-body:
     - meta_include_prototype: false
@@ -1967,8 +1980,7 @@ contexts:
 ###[ PROTOTYPES ]#############################################################
 
   bol-pop:
-    # Note: empty lines are ignored
-    - match: ^(?!$)
+    - match: ^
       pop: 1
 
   else-pop:
@@ -1983,7 +1995,14 @@ contexts:
   line-continuations:
     - match: \^\n
       scope: punctuation.separator.continuation.line.dosbatch
-      push: bol-pop
+      push: line-continuation-body
+
+  line-continuation-body:
+    # The first linefeed diretly following a continuation is treated literal.
+    # Note: Must consume \n to work.
+    - match: ^\n
+      set: bol-pop
+    - include: bol-pop
 
   eoc-pop:
     # Note: An end of command appears in unquoted regions only!

Batch File/tests/syntax_test_batch_file.bat

@@ -47,6 +47,11 @@
    not a comment
 :: ^^^^^^^^^^^^^^ - comment
 
+   REM ^
+   Line^
+   continuation after first token
+:: ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ meta.command.rem.dosbatch comment.line.rem.dosbatch
+
 REM
    not a comment
 :: ^^^^^^^^^^^^^^ - comment
@@ -59,6 +64,31 @@ REM This & and | echo "is commented out" ^
 :: <- keyword.declaration.rem.dosbatch
 ::  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ meta.command.rem.dosbatch comment.line.rem.dosbatch
 
+REM Line^
+continuation
+:: <- meta.command.rem.dosbatch comment.line.rem.dosbatch
+:: ^^^^^^^^^^ meta.command.rem.dosbatch comment.line.rem.dosbatch
+
+REM Line^
+
+continuation
+:: <- meta.command.rem.dosbatch comment.line.rem.dosbatch
+:: ^^^^^^^^^^ meta.command.rem.dosbatch comment.line.rem.dosbatch
+
+REM Line^
+
+continuation^
+not a comment
+:: <- - comment
+:: ^^^^^^^^^^ - comment
+
+REM Line^
+
+
+not a comment
+:: <- - comment
+:: ^^^^^^^ - comment
+
 REM No line ^
 continuation
 :: <- - comment
@@ -481,6 +511,22 @@ ECHO : Not a comment ^
 :: ^ punctuation.definition.variable.dosbatch
 :: ^^^^ variable.label.dosbatch - keyword
 
+   CALL ^
+
+   :EOF
+:: ^^^^ meta.function-call.identifier.dosbatch
+::     ^ - meta.function-call
+:: ^ punctuation.definition.variable.dosbatch
+:: ^^^^ variable.label.dosbatch - keyword
+
+   CALL ^
+
+
+   :EOF
+:: ^^^^ - meta.function-call
+:: ^ punctuation.definition.label.dosbatch
+:: ^^^^ entity.name.label.dosbatch
+
    CALL :foo 10 %1
 ::^ - meta.function-call
 :: ^^^^^ meta.function-call.dosbatch