[LyX/master] If lyx2lyx is asked to convert a file to the format it already is, then just perform a null conversion. This seems better than aborting with an error. I can imagine a script that converted all files in a certain directory to format 498, and you don't want it to be an error if one of them is already 498.

[Richard Heck]

commit 221932f63a230e0cc01d5581c3521128d8d12e2f
Author: Richard Heck <rgh...@lyx.org>
Date:   Sun Nov 1 16:27:58 2015 -0500

    If lyx2lyx is asked to convert a file to the format it already is,
    then just perform a null conversion. This seems better than aborting
    with an error. I can imagine a script that converted all files in a
    certain directory to format 498, and you don't want it to be an error
    if one of them is already 498.
    
    Prior to this, what lyx2lyx would do is convert to the lowest format
    in the current version. So, e.g., asked to convert 498 to 498 it would
    convert to 474. That is obviously wrong.

diff --git a/lib/lyx2lyx/LyX.py b/lib/lyx2lyx/LyX.py
index 04acb24..700a699 100644
--- a/lib/lyx2lyx/LyX.py
+++ b/lib/lyx2lyx/LyX.py
@@ -553,6 +553,9 @@ class LyX_base:
 
     def convert(self):
         "Convert from current (self.format) to self.end_format."
+        if self.format == self.end_format:
+            return
+
         mode, conversion_chain = self.chain()
         self.warning("conversion chain: " + str(conversion_chain), 3)