datasette serve when invoked with --reload interprets the serve command as a file #2123
Description
When running datasette serve with the --reload flag, the serve command is picked up as a file argument:
$ datasette serve --reload test_db
Starting monitor for PID 13574.
Error: Invalid value for '[FILES]...': Path 'serve' does not exist.
Press ENTER or change a file to reload.
If a 'serve' file is created it launches properly (albeit with an empty database called serve):
$ touch serve; datasette serve --reload test_db
Starting monitor for PID 13628.
INFO: Started server process [13628]
INFO: Waiting for application startup.
INFO: Application startup complete.
INFO: Uvicorn running on http://127.0.0.1:8001 (Press CTRL+C to quit)
Version (running from HEAD on main):
$ datasette --version
datasette, version 1.0a2
This issue appears to have existed for awhile as #1380 (comment) mentions the error in a different context.
I'm happy to debug and land a patch if it's welcome.