skpdiff: remove default value for output. Diifs can be very big, and fill a hard drive, no sense to…

tools/skpdiff/skpdiff_main.cpp

Index: tools/skpdiff/skpdiff_main.cpp
===================================================================
--- tools/skpdiff/skpdiff_main.cpp	(revision 10286)
+++ tools/skpdiff/skpdiff_main.cpp	(working copy)
@@ -37,7 +37,7 @@
 DEFINE_string2(differs, d, "", "The names of the differs to use or all of them by default");
 DEFINE_string2(folders, f, "", "Compare two folders with identical subfile names: <baseline folder> <test folder>");
 DEFINE_string2(patterns, p, "", "Use two patterns to compare images: <baseline> <test>");
-DEFINE_string2(output, o, "skpdiff_output.json", "Writes the output of these diffs to output: <output>");
+DEFINE_string2(output, o, "", "Writes the output of these diffs to output: <output>");
 DEFINE_bool(jsonp, true, "Output JSON with padding");
 DEFINE_string(csv, "", "Writes the output of these diffs to a csv file");