With the .sublime-syntax
format, how would you match the following:
This is a title
===============
This is valid Markdown and AsciiDoc, and maybe also reStructuredText.
How would you match this as a section heading? This is a title
here, without knowing the next line, could also be the beginning of a paragraph, hence the challenging ambiguity: at this point, you can't make it part of a heading scope.
This is currently not possible, which is why the Markdown syntax definition that ships with ST can only scope the underline characters as a heading, and not the heading text itself.
There is a feature request for multiline match support in .sublime-syntax
files here: https://github.com/SublimeTextIssues/Core/issues/1693