highlight: ignore Unicode's extra linebreaks (issue4291)

Unicode and Python's unicode.splitlines() treat several extra legacy
ASCII codepoints as linebreaks, even though the vast bulk of computing
and Python's own str.splitlines() do not. Rather than introduce line
numbering confusion, we filter them out when highlighting.

hgext/highlight/highlight.py

@@ -1,62 +1,67 b''
 # highlight.py - highlight extension implementation file
 #
 #  Copyright 2007-2009 Adam Hupp <[e-mail]> and others
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 #
 # The original module was split in an interface and an implementation
 # file to defer pygments loading and speedup extension setup.
 
 from mercurial import demandimport
 demandimport.ignore.extend(['pkgutil', 'pkg_resources', '__main__'])
 from mercurial import util, encoding
 
 from pygments import highlight
 from pygments.util import ClassNotFound
 from pygments.lexers import guess_lexer, guess_lexer_for_filename, TextLexer
 from pygments.formatters import HtmlFormatter
 
 SYNTAX_CSS = ('\n<link rel="stylesheet" href="{url}highlightcss" '
               'type="text/css" />')
 
 def pygmentize(field, fctx, style, tmpl):
 
     # append a <link ...> to the syntax highlighting css
     old_header = tmpl.load('header')
     if SYNTAX_CSS not in old_header:
         new_header =  old_header + SYNTAX_CSS
         tmpl.cache['header'] = new_header
 
     text = fctx.data()
     if util.binary(text):
         return
 
+    # str.splitlines() != unicode.splitlines() because "reasons"
+    for c in "\x0c\x1c\x1d\x1e":
+        if c in text:
+            text = text.replace(c, '')
+
     # Pygments is best used with Unicode strings:
     # <http://pygments.org/docs/unicode/>
     text = text.decode(encoding.encoding, 'replace')
 
     # To get multi-line strings right, we can't format line-by-line
     try:
         lexer = guess_lexer_for_filename(fctx.path(), text[:1024],
                                          stripnl=False)
     except (ClassNotFound, ValueError):
         try:
             lexer = guess_lexer(text[:1024], stripnl=False)
         except (ClassNotFound, ValueError):
             lexer = TextLexer(stripnl=False)
 
     formatter = HtmlFormatter(style=style)
 
     colorized = highlight(text, lexer, formatter)
     # strip wrapping div
     colorized = colorized[:colorized.find('\n</pre>')]
     colorized = colorized[colorized.find('<pre>') + 5:]
     coloriter = (s.encode(encoding.encoding, 'replace')
                  for s in colorized.splitlines())
 
     tmpl.filters['colorize'] = lambda x: coloriter.next()
 
     oldl = tmpl.cache[field]
     newl = oldl.replace('line|escape', 'line|colorize')
     tmpl.cache[field] = newl