Several commands continued to support the legacy positional path
argument to specify a working directory. This functionality has been
replaced with the global -chdir flag, which is specified before any
other arguments, including the sub-command name.
This commit removes support for the trailing path parameter from
most commands. The only command which still supports a path argument is
fmt, which also supports "-" to indicate receiving configuration from
standard input.
Any invocation of a command with an invalid trailing path parameter will
result in a short error message, pointing at the -chdir alternative.
There are many test updates in this commit, almost all of which are
migrations from using positional arguments to specify a working
directory. Because of the layer at which these tests run, we are unable
to use the -chdir argument, so the churn in test files is larger than
ideal. Sorry!
Validation is the best time to return detailed diagnostics
to the user since we're much more likely to have source
location information, etc than we are in later operations.
This change doesn't actually add any detail to the messages
yet, but it changes the interface so that we can gradually
introduce more detailed diagnostics over time.
While here there are some minor adjustments to some of the
messages to improve their consistency with terminology we
use elsewhere.
