Fix a typo.  Thanks to Dominique Pellé for pointing it out.
    
        | author | Steve Losh <steve@stevelosh.com> | 
    
        | date | Sat, 08 Sep 2012 13:45:55 -0400 | 
    
    
        | parents | ba2b338cf6d5 | 
    
        | children | fcbfb7d92770 | 
    
        | branches/tags | (none) | 
    
        | files | chapters/49.markdown | 
Changes
    
--- a/chapters/49.markdown	Sat Sep 08 13:45:05 2012 -0400
+++ b/chapters/49.markdown	Sat Sep 08 13:45:55 2012 -0400
@@ -245,7 +245,7 @@
 If the current line has some non-whitespace characters it won't match and we'll
 just return `'0'` as before.
 
-If the current line *does* match the regex (i.e. is it's empty or just
+If the current line *does* match the regex (i.e. if it's empty or just
 whitespace) we return the string `'-1'`.
 
 Earlier I said that a line's foldlevel can be zero or a positive integer, so