This takes all of the functions that look up simple data about
paths (such as `git_futils_isdir`) and moves them over to path.h
(becoming `git_path_isdir`). This leaves fileops.h just with
functions that actually manipulate the filesystem or look at
the file contents in some way.
As part of this, the dir.h header which is really just for win32
support was moved into win32 (with some minor changes).
The ownership semantics have been changed all over the library to be
consistent. There are no more "borrowed" or duplicated references.
Main changes:
- `git_repository_open2` and `3` have been dropped.
- Added setters and getters to hotswap all the repository owned
objects:
`git_repository_index`
`git_repository_set_index`
`git_repository_odb`
`git_repository_set_odb`
`git_repository_config`
`git_repository_set_config`
`git_repository_workdir`
`git_repository_set_workdir`
Now working directories/index files/ODBs and so on can be
hot-swapped after creating a repository and between operations.
- All these objects now have proper ownership semantics with
refcounting: they all require freeing after they are no longer
needed (the repository always keeps its internal reference).
- Repository open and initialization has been updated to keep in
mind the configuration files. Bare repositories are now always
detected, and a default config file is created on init.
- All the tests affected by these changes have been dropped from the
old test suite and ported to the new one.
