Before, it was a general setting and couldn't be customized for the shortInstrumentName any longer. Also, extend regtest incipit.ly to actually cover \incipit and check for shortInstrumentName's self-alignment-X setting. Some reformating there.
Actually there is still some difference in aligning instrumentName and shortInstrumentName. I suspect it is related to padding. Worth further investigation, but beyond the scope of this patch.
Closes #6108 (closed)