Introduce the repository object 'struct repository' which can be used to
hold all state pertaining to a git repository.
Some of the benefits of object-ifying a repository are:
1. Make the code base more readable and easier to reason about.
2. Allow for working on multiple repositories, specifically
submodules, within the same process. Currently the process for
working on a submodule involves setting up an argv_array of options
for a particular command and then launching a child process to
execute the command in the context of the submodule. This is
clunky and can require lots of little hacks in order to ensure
correctness. Ideally it would be nice to simply pass a repository
and an options struct to a command.
3. Eliminating reliance on global state will make it easier to
enable the use of threading to improve performance.
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
