Simplify scan_for_server and deprecate ancient TREES config.

Review Request #11478 — Created Feb. 19, 2021 and updated


The steps involved in the various repository tool scan_for_server
implementations were overcomplicated and ugly. The main command would
check the option (which includes the config value), and then failing
that, delegate to the repository tool. The repository tools would then
check the config value again before scanning any repository-specific
storage locations like SVN attributes or P4 counters. This second config
step also looked in the TREES config key, which was something from
extremely early on in RBTools' life and has never been properly
documented or expanded upon in the intended ways.

This change cleans up the individual tool scan_for_server
implementations to only perform checking repository-specific methods.
The check for the TREES config has been moved to the very end of the
process as a fallback, and will emit a warning that such a configuration
is deprecated and will be removed.

  • Ran unit tests.
  • Set up a configuration that used the old TREES method and saw the
    expected warning.
Simplify scan_for_server and deprecate ancient TREES config.
Checks run (2 succeeded)
flake8 passed.
JSHint passed.