Add the ability to create blob given a provider of chunks of bytes

Fix compilation warning and failing test

git_status_file returns GIT_ENOTFOUND for "域名检测工具.exe" (and similarly named files) 

git_status_file would always return GIT_ENOTFOUND for these files.

The underlying bug was that git__strcmp_cb, which is used by
git_path_with_stat_cmp to sort entries in the working directory,
compares strings based on unsigned chars (this is confirmed by the
strcmp(3) manpage), while git__prefixcmp, which is used by
workdir_iterator__entry_cmp to search for a path in the working
directory, compares strings based on char. So the sort puts this path at
the end of the list, while the search expects it to be at the beginning.

The fix was simply to make git__prefixcmp compare using unsigned chars,
just like strcmp(3). The rest of the change is just adding/updating
tests.

Add HTTPS support

Make git_repository_init() value "core.filemode" and "core.ignorecase"

libgit2-glib bindings moved to gnome servers

config: do not set an error for GIT_ENOTFOUND

Remotes and refspecs

Fix git_remote_connected

Fix checking for the presence of a flag

Enable mingw cross-compilation in travis-ci

Two things:
1) By default, Linux CMake puts -fPIC on the link line. So we remove that
for MINGW to avoid warnings that it will be ignored.
2) Similarly, move -fvisibility=hidden flag to be for non-mingw
compilation only to avoid warnings that it will be ignored.

Otherwise we can't cross-compile on Linux.

Sometimes it's useful not to perform the check. Allow it to be
configurable.

tests-clar/core: fix non-null warning

gcc 4.7.0 apparently doesn't see that we won't call setenv with NULL as
second argument.

The error codes from failed lookups of system and global files
on Windows were not consistent with the codes returned on other
platforms.  This makes the error detection patterns match and
adds a unit test for the various errors.

Fix bugs for status

This fixes two bugs:

* Issue #728 where git_status_file was not working for files
  that contain spaces.  This was caused by reusing the "fnmatch"
  parsing code from ignore and attribute files to interpret the
  "pathspec" that constrained the files to apply the status to.
  In that code, unescaped whitespace was considered terminal to
  the pattern, so a file with internal whitespace was excluded
  from the matched files.  The fix was to add a mode to that code
  that allows spaces and tabs inside patterns.  This mode only
  comes into play when parsing in-memory strings.

* The other issue was undetected, but it was in the recently
  added code to reload gitattributes / gitignores when they were
  changed on disk.  That code was not clearing out the old values
  from the cached file content before reparsing which meant that
  newly added patterns would be read in, but deleted patterns
  would not be removed.  The fix was to clear the vector of
  patterns in a cached file before reparsing the file.

windows: Properly expand all environment variables