index: Enhance documentation
index: Fix indentations
reset: Enhance documentation
Allow progress callback to cancel fetch

This works by having the indexer watch the return
code of the callback, so will only take effect
on object boundaries.
reset: Introduce git_reset_default()
tests: Remove useless code
Fix MSVC compilation warnings

Fix #1308
Document callback-triggered cancellation
Enhance test coverage for transfer cancellation
Allow all non-zero returns to cancel transfers
Expect standard error code from internal calls
removed other references to api.html
Call p_readlink to determine symlink size
Return the matched pathspec pattern in `git_pathspec_match_path`

Instead of returning directly the pattern as the return value, I used an
out parameter, because the function also tests if the passed pathspecs
vector is empty. If yes, it considers that the path "matches", but in
that case there is no matched pattern per se.
diff: add a notify callback to `git_diff__from_iterators`

The callback will be called for each file, just before the `git_delta_t` gets inserted into the diff list.

When the callback:
- returns < 0, the diff process will be aborted
- returns > 0, the delta will not be inserted into the diff list, but the diff process continues
- returns 0, the delta is inserted into the diff list, and the diff process continues
Fix call to readlink
Include <string.h>
Replace call to strnlen with call to strlen
Replace LoadLibrary with GetModuleHandle, since kernel32 is loaded by default

As requested
Moved braces to conform to code style