reconsider 'pretty_setmargin' as "control" command (instead of "diag") -- it is stateful and Proof General legacy;

 src/Pure

 src/FOL

 src/HOL

 src/ZF

 src/CCL

 src/CTT

 src/Cube

 src/FOLP

 src/LCF

 src/Sequents

 src/Doc