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 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.
For the transition, http is going to keep its own logic until the
git/common code catches up with the implied multi_ack that http
has. This also has the side-effect of making the code cleaner and more
correct regardingt he protocol.
There are three actual changes in this commit:
1. When the trailing newline of a file is removed in a diff, the
change will now be reported with `GIT_DIFF_LINE_DEL_EOFNL` passed
to the callback. Previously, the `ADD_EOFNL` constant was given
which was just an error in my understanding of when the various
circumstances arose. `GIT_DIFF_LINE_ADD_EOFNL` is deprecated and
should never be generated. A new newline is simply an `ADD`.
2. Rewrote the `diff_delta__merge_like_cgit` function that contains
the core logic of the `git_diff_merge` implementation. The new
version doesn't actually have significantly different behavior,
but the logic should be much more obvious, I think.
3. Fixed a bug in `git_diff_merge` where it freed a string pool
while some of the string data was still in use. This led to
`git_diff_print_patch` accessing memory that had been freed.
The rest of this commit contains improved documentation in `diff.h`
to make the behavior and the equivalencies with core git clearer,
and a bunch of new tests to cover the various cases, oh and a minor
simplification of `examples/diff.c`.
