Duplicate tree entries

Topic/explicit index errors

Fixes for two segfaults

config: make git_config_open_level() work with an empty config

Fix libgit2/libgit2sharp#243

Valgrind reports Invalid Read when the configuration file contains some empty line

Update documentation in remote.h

Basic authentication for http and winhttp

- Update 'tests-clar/resources/config/config11' in order to reproduce the invalidread with the unittest (just added some \n at the end of the file)
- Fix config_file.c

Correctly parse tags lacking a description

Fix compilation for mingw32 and cygwin

inet_pton is available only in windows vista or later,
fixed the issue by reimplementing it using WSAStringToAddress

fetch: Write packs to the ODB instead of directly to disk

Bail out of remote loading if the URL would be NULL

Apparently git_remote_list() includes even remotes for which git_remote_load() would fail. Sorry @nulltoken, false alarm.

This reverts commit f358ec14.

CC @nulltoken

Fix state when HEAD is not detached

Let the user grab the packfile as it's being written

This fixes a crash from attempting to invoke git__strdup() against NULL.