$ darcs init
$ darcs diff | od -c
$ darcs diff x | od -c
diff: old-eat/x: No such file or directory
diff: new-eat/x: No such file or directory
$ # putting stderr to null for the rest for brevity
$ darcs diff x y 2> /dev/null | od -c
0000000   \n                                                            
0000001
$ darcs diff x y z 2> /dev/null | od -c
0000000   \n  \n                                                        
0000002
$ darcs diff x y z p 2> /dev/null | od -c
0000000   \n  \n  \n                                                    
0000003
$ darcs diff x y z p d 2> /dev/null | od -c
0000000   \n  \n  \n  \n                                                
0000004
$ darcs diff x y z p d q 2> /dev/null | od -c
0000000   \n  \n  \n  \n  \n                                            
0000005

This is causing problems with a script I have that does "darcs diff -u
$files" and then tries to use the output as input for "patch". Patch
doesn't mind empty files but it doesn't like files that have a non-zero
length but no actual patch.

This issue is claimed to be resolved by this patch:

"Resolve issue2067: inexsitant files result in empty lines in darcs"

The following patch sent by Florent Becker <florent.becker@ens-lyon.org> updated issue issue2067 with
status=resolved;resolvedin=2.8.0 HEAD

* Resolve issue2067: inexsitant files result in empty lines in darcs 
Ignore-this: 955ca17ff9d2bd51b36934de76f51d70