Squashed 'deps/libgit2/' changes from 9b87998..59e3f45

59e3f45 Merge pull request #2487 from libgit2/cmn/revwalk-no-prealloc
b62a6a1 array: mark the array to grow as volatile
9746b36 revwalk: remove preallocation of the uninteresting commits
9de6ec5 Merge pull request #2477 from ethomson/merge
243db06 Merge pull request #2484 from libgit2/fix-git-status-list-new-unreadable-folder
85b7268 undo indentation change in diff_print.c
bf9a7e0 Merge pull request #2485 from ethomson/cherrypick
0ba4dca git_cherry_pick -> git_cherrypick
7d0ab0f Merge remote-tracking branch 'origin/master' into fix-git-status-list-new-unreadable-folder
e824e63 Remove debug printfs.
35b1471 Move the UNREADABLE enums to the correct group.
994404b Don't allow conflicts by default
091165c Merge pull request #2475 from libgit2/expose-buffer-binary-detection
b3af2d8 Just put it all in buffer.
ec813d8 Merge pull request #2476 from linquize/config-lf-eof
8baeb8a ssh: Fix unused warning
84a85d1 clone: should_clone? Of course we should clone. That's not the question
ed99e0b Merge pull request #2467 from ethomson/win_local_clone
6937486 Add unit test to test add section without lf at EOF
991dab2 Make sure \n is at the end of config file before a new section is written
df4cba0 Export git_buf_text_is_binary and git_buf_text_contains_nul.
ad08250 Merge pull request #2472 from jacquesg/perl-link
851ae37 Merge pull request #2474 from ethomson/clar_file_report
3d997dc Switch description and path reporting
2ef20da Updated perl bindings link
529fd30 Handle local file:/// paths on Windows
a6d7e16 Merge pull request #2466 from jacquesg/win2003-platform-sdk
44cfb6f Merge pull request #2463 from libgit2/cmn/ssh-factory-for-paths
863dabd Merge pull request #2465 from libgit2/cmn/refspec-start-middle
356b891 Merge pull request #2468 from Airbitz/pack-error-reporting
0dbbfbb Merge pull request #2457 from ethomson/merge_fix
eb5f034 checkout: fix docs formatting for the options
4edd1a0 Merge remote-tracking branch 'origin/development' into fix-git-status-list-new-unreadable-folder
01b432c Properly report failure when expanding a packfile
02bf955 merge: don't open COMMIT_MSG unless we need to append conflicts
18eb6ec Documentation fixes
d4256ed ssh: provide a factory function for setting ssh paths
59ceb43 Define IO_REPARSE_TAG_SYMLINK if its not defined by WinNT.h
7209051 Secure CRT is only available from Visual Studio 2005+
491ad0d qsort_r is only available from Visual Studio 2005+
cde32d4 Variadic macros is only available from Visual Studio 2005+
ab864e9 _stat64 is a function, __stat64 is the structure
b8365f2 strnlen() is only available from Visual Studio 2005+
90c2b37 in_addr is defined in <Winsock2.h>, include before <ws2tcpip.h>
9fef46d Add a CHANGELOG entry for refspecs with asterisk in the middle
f5287fa refspec: support asterisks in the middle of a pattern
9ed104a refspec: short-circuit non-pattern refspecs on transform
9e2d2f3 Whitespace wibbles.
dc49e1b Merge remote-tracking branch 'origin/development' into fix-git-status-list-new-unreadable-folder
54c02d2 Clear out the struct.
a576a34 Add another test for unreadable and not included.
5e65420 Implement GIT_DIFF_INCLUDE_UNREADABLE_AS_UNTRACKED
7b491a7 GIT_DIFF_INCLUDE_UNREADABLE_AS_UNTRACKED
79d5b5c Add GIT_STATUS_OPT_INCLUDE_UNREADABLE_AS_UNTRACKED
523553f Fix the no permissions test.
59fceba Use 'X' for unreadable status.
6627192 Add GIT_STATUS_OPT_INCLUDE_UNREADABLE
a777fc3 Remove GIT_FILEMODE_NEW as it's unused.
c3252c1 We do expect the foo path in the nopermissions test
c436609 Don't need to duplicate this code.
7c4bbbf Try a value for UNREADABLE that won't get masked out?!
e8cc303 Return GIT_DELTA_UNREADABLE for a file with a mode change
6580b11 Remove errant newline
9532edc Simplify the no permission test.
9067d5a Remove errant whitespace.
86c9d3d Return GIT_FILEMODE_UNREADABLE for files that fail to stat.
61bef72 Start adding GIT_DELTA_UNREADABLE and GIT_STATUS_WT_UNREADABLE.
f47bc8f Skip unreadable files for now.
9055347 Rename GIT_ENOACCESS -> GIT_EUNREADABLE
dc4906f Skip unreadable files for now.
158c8ba Return a specific error for EACCES.
8d3a2d5 Simplify the test.
2b5a99d Add a test (failing) for a work tree status.

git-subtree-dir: deps/libgit2
git-subtree-split: 59e3f45b6150984e6a74ce79062caa459eda369f
Merge commit '29fe659b35df78c65841de2ce614c6324203600c' into jacquesg/update-libgit2
Minor fixes due to libgit2 upgrade

* New: GIT_DELTA_UNREADABLE
* Changed: GIT_FILEMODE_NEW -> GIT_FILEMODE_UNREADABLE
Revert "Build WinHTTP on Windows" (libgit2 not quite ready yet)

This reverts commit 64da67f7061721b347f9312f0f71eea65c5338dd.
Changes: update