When diffs are generated, the value for the 'nfiles' field of 'git_diff_delta'
will be consistent with the value in the 'status' field. Merging diffs can
modify the 'status' field of some deltas and the 'nfiles' field needs to be
updated accordingly.

Clear temporary buffer when filtering

If we are using a temporary buffer for filtering, be sure to clear
it before using it, in case the file that we are filtering is empty.

squash some leaks

Add a custom param to git_smart_subtransport_definition

WinHTTP for MinGW

note: use a git_buf to return the default namespace

examples: add remote example.

checkout: report correct invalid path

In case of a bad url or other error during the connection setup, we
close the stream via free.

fix changelog

mkdir-ext: Assume directories don't exist; fix all race cases

win32 resource: allow custom comments field in DLL

Allow merges of files (and trees) with whitespace problems/fixes

The smart transport has already take the payload param. For the
sub transport a payload param is useful for the implementer.

clar: update to 08f434d

Update tips fixes

Lower case the include directive of windows header

PERF: In MERGE, lazily compute is_binary

Initialize refs vector in git_remote_update_tips().

Otherwise, bailing out early when ls_to_vector() fails accesses
uninitialized memory.

The caller has otherwise no way to know how long the string will be
allocated or ability to free it.

This fixes #2944.

Add annotated versions of ref-modying functions

[WIP] Smarter pack-building

Don't ask for a stream's certificate unless it's encrypted

Fix git_submodule_sync writing URL to wrong key.

Since the Linux platform has a case sensitive file system, the header name should be lower case for cross compiling purposes. (On Linux, the mingw header is called ```windows.h```).