This is a major rework of the remote repository detection mechanism

within RBTools. The old implementation had a lot of issues, worst of

which was that there was a lot of inconsistency across different tool

implementations (for example, rbt post had a lot of additional

detection code that wasn't shared with other tools).
In the new implementation, we first try to fetch remote repositories,

filtering by the configured repository name, or detected repository

path(s). If this returns a single result, we can immediately return

that. If that fails, it means we're in a situation where the configured

paths on the server are different from the local path (including any

mirror_path), and we need to match in a different way. Individual tools

may implement find_matching_server_repository in order to do

tool-specific comparisons (which right now is done by SVN with

repository UUID and ClearCase with VOB UUID). This new method replaces

the old RepositoryInfo.find_server_repository_info method, which

always felt super ugly and clunky. In lieu of that, RepositoryInfo

subclasses can implement update_from_remote, which allows them to

include information from the remote repository or repository info

resource.
Commands which want to make use of the repository can now set the

needs_repository attribute. In this case, the command initialization

will handle finding the remote repository and updating the

RepositoryInfo appropriately. This corrects a couple issues where

commands were using the repository but forgetting to call the old

find_server_repository_info, potentially ending up with incorrect

data. The setup-repo command works a little differently because it

needs to potentially do that multiple times, but it uses the same

underlying mechanism to attempt to pre-filter the list of matching

repositories in a useful way.
This includes several other improvements and cleanups along the way:

Various places that fetch repositories to find matches have all been

  updated to use the locally detected tool to filter the response from

  the server. In the case where the server has a mix of repository

  types, this will dramatically improve the results.
rbt setup-repo's server initialization has been fixed to merge

  handling of --server and interactive entry. This both improves the

  code, and has the side effect of making it so that if the server

  specified on the command line doesn't work, it will prompt the user.

Ran unit tests.
Verified that repository match fetches properly passed tool= for API

  requests to filter the responses based on the locally detected tool.
rbt land: Tested basic behavior.
rbt patch: Tested basic behavior.
rbt post: Posted new and updated changes against Git, including with

-u. Created a remote SVN repository and posted purely remote commits

  using --repository-url.
rbt setup-repo: Tested with both --server and specifying the

  server name interactively.
rbt stamp: Tested basic behavior.
rbt status: tested both with and without --all. Verified that

  repository detection was making the most minimal API requests possible

  based on various .reviewboardrc configurations.