The flag.Lookup("test.v") check existed to skip opening a browser
during tests, but the tests don't exercise RunE, so this was never
used. The --no-open-browser flag is sufficient on its own.
Bind the RC server to localhost:0 and read the bound URL back via a
new rcserver.Server.URLs() accessor instead of pre-allocating a port
in cmd/gui. This removes the small TOCTOU race window between
freePort() closing its listener and rcserver claiming the same port.
- Fail gracefully if `make fetch-gui` hasn't been run
- Return errors instead of panic or fatal errrors
- Don't run `make fetch-gui` on every make since we have it in the workflow
This adds a new gui command which runs an embedded copy of the GUI at
https://github.com/rclone/rclone-web/
The GUI release is fetched as part of the CI build.
