[tex-live] Undocumented change in fmtutil --enablefmt/--disablefmt

[Ken Brown]

In TL2014, the commands 'fmtutil-sys --enablefmt cont-en' and 'fmtutil-sys 
--disablefmt cont-en' would enable/disable both cont-en formats (one with engine 
pdftex, the other with engine xetex).

This has changed in TL2015:

$ fmtutil-sys --enablefmt cont-en
fmtutil: fmtutil is using the following fmtutil.cnf files (in precedence order):
fmtutil:   /usr/local/texlive/2015/texmf-config/web2c/fmtutil.cnf
fmtutil:   /usr/local/texlive/2015/texmf-dist/web2c/fmtutil.cnf
fmtutil: fmtutil is using the following fmtutil.cnf file for writing changes:
fmtutil:   /usr/local/texlive/2015/texmf-config/web2c/fmtutil.cnf
fmtutil [WARNING]: More engines given for format cont-en.
fmtutil [WARNING]: Please specify one of the engines: xetex pdftex
fmtutil [WARNING]: No changes done.

Neither the error message nor the fmtutil help text explains *how* to specify 
the engine (by using the syntax "format/engine").  I suggest adding this 
information.  In the case of the help text, you should probably mention both

   --enablefmt FORMATNAME

and

   --enablefmt FORMATNAME/ENGINENAME

and say that the second form is mandatory if FORMATNAME occurs in fmtutil.cnf 
with more than one engine.

Ken