This edit https://commons.wikimedia.org/wiki/Special:Diff/309221779 holds the summary line "Imported with FileImporter from …". Technically, this is supposed to be a null edit with no changes, only with this summary line. But it contains two changes: The HTML comment `<!--This file was moved here using FileImporter from …-->` is added to the top, and the template replacements are made.
The next edit https://commons.wikimedia.org/wiki/Special:Diff/309221781 holds the summary line "Replaced 1 template names with Wikimedia Commons template names".
Reported at T194505#4391840.
Another worst-case example: In http://mwfileimport.wmflabs.org/wiki/index.php?title=File:Stolperstein_f%C3%BCr_Lina_Speiser,_Br%C3%BCckenstrasse_11,_Bad_Cannstatt,_Stuttgart.JPG&curid=105&action=history the summary line "Replaced … template names with … template names" got lost entirely, because the edit was empty (the user did not made additional edits).
 The template replacements must be made in the next revision.
 The summary line should not get lost.
 The HTML comment should also be added in the next revision.
 The null revision should only contain the title change (if one was made).