patch: don't separate \r and \n when colorizing diff output

When displaying diffs, \r at the end of a line is treated as trailing
whitespace. This causes an ANSI escape code to be inserted between \r and \n.
Some programs, such as less since version 530 (maybe earlier, but at least not
version 487) displays ^M when it encounters a lone \r. This causes a lot of
noise in diff output on Windows, where \r\n is used to terminate lines.

We avoid that by treating both \n and \r\n as end of line when considering
trailing whitespace.

mercurial/patch.py

@@ -2405,7 +2405,7 b' def diffsinglehunk(hunklines):'
     """yield tokens for a list of lines in a single hunk"""
     for line in hunklines:
         # chomp
-        chompline = line.rstrip('\n')
+        chompline = line.rstrip('\r\n')
         # highlight tabs and trailing whitespace
         stripline = chompline.rstrip()
         if line.startswith('-'):
@@ -2473,6 +2473,9 b' def diffsinglehunkinline(hunklines):'
             isendofline = token.endswith('\n')
             if isendofline:
                 chomp = token[:-1] # chomp
+                if chomp.endswith('\r'):
+                    chomp = chomp[:-1]
+                endofline = token[len(chomp):]
                 token = chomp.rstrip() # detect spaces at the end
                 endspaces = chomp[len(token):]
             # scan tabs
@@ -2488,7 +2491,7 b' def diffsinglehunkinline(hunklines):'
             if isendofline:
                 if endspaces:
                     yield (endspaces, 'diff.trailingwhitespace')
-                yield ('\n', '')
+                yield (endofline, '')
                 nextisnewline = True
 
 def difflabel(func, *args, **kw):