This fixes some missed places where we can apply const-ness to
various public APIs.
There are still some index and tree APIs that cannot take const
pointers because we sort our `git_vectors` lazily and so we can't
reliably bsearch the index and tree content without applying a
`git_vector_sort()` first.
This also fixes some missed places where size_t can be used and
where const can be applied to a couple internal functions.
This makes the diff functions that take callbacks both take
the payload parameter after the callback function pointers and
pass the payload as the last argument to the callback function
instead of the first. This should make them consistent with
other callbacks across the API.
A number of diff APIs and the `git_checkout_index` API take a
`git_repository` object an operate on the index. This updates
them to take a `git_index` pointer explicitly and only fall back
on the `git_repository` index if the index input is NULL. This
makes it easier to operate on a temporary index.
This fixes a number of warnings and problems with cross-platform
builds. Among other things, it's not safe to name a member of a
structure "strcmp" because that may be #defined.
This is a major reworking of checkout strategy options. The
checkout code is now sensitive to the contents of the HEAD tree
and the new options allow you to update the working tree so that
it will match the index content only when it previously matched
the contents of the HEAD. This allows you to, for example, to
distinguish between removing files that are in the HEAD but not
in the index, vs just removing all untracked files.
Because of various corner cases that arise, etc., this required
some additional capabilities in rmdir and other utility functions.
This includes the beginnings of an implementation of code to read
a partial tree into the index based on a pathspec, but that is
not enabled because of the possibility of creating conflicting
index entries.
This improves docs in some of the public header files, cleans
up and improves some of the example code, and fixes a couple
of pedantic warnings in places.
