Build the current document and rebuild it as input files change.
tectonic -X watch [--exec <execute>...] [-x <execute>...]
This command builds the current document in the same fashion as
tectonic -X build, and then stays running and watches for changes to the input
files. It rebuilds the document when changes are detected.
--exec option (or
-x for short) configures the command used to run the
document build. The value of this option is appended to
tectonic -X and
build. If you want to pass options to the build command, this is
the way to do so.