A connection string can carry global.* options which change rclone's
process-wide configuration (e.g. global.http_proxy). This is
undesirable for the rc interface which was designed to have multiple
users or connections at once. The rc interface has the `_config`
mechanism for setting request scoped global config.
This blocks global.* options on all rc paths by marking the context as
a remote control request at the rc boundaries. fs.NewFs then skips
applying global.* to the process-wide config for a marked context.
The marker is reapplied in fs.CopyConfig, which is the call rclone
uses to detach context but keep config.
global.* options still apply to the individual backend they are set
on, exactly like override.* options; they just no longer leak into the
rest of the process. Remotes created directly on the command line are
unaffected as are remotes defined in the config file.
See: GHSA-qw24-gh76-8rvv
53f972830c