When comparing 2 *.glyphs files using MergeGlyphs.app, you usually open them from GUI.
With other application like FileMerge.app, I sometimes open the file(s) using following command from Terminal.app:
open -a <Application> <file(s)>
I did it with the MergeGlyphs.app with 2 glyphs files, but MergeGlyphs.app opens the 2 .glyphs file to 2 separate compare window and each window loaded only 1 glyphs file (i.e. no comparing counterpart loaded) like:
open -a MergeGlyphs.app Font-01.glyphs Font-02.glyphs
Is there any solution or workaround of this kind of operation?