Add unit tests to confirm ignore directory pattern matches and
to confirm that ignore and attribute files are loaded properly
into the attribute file cache.
Per issue #533, the handling of relative paths in attribute
and ignore files was not right. Fixed this by pre-joining
the relative path of the attribute/ignore file onto the match
string when a full path match is required.
Unfortunately, fixing this required a bit more code than I
would have liked because I had to juggle things around so that
the fnmatch parser would have sufficient information to prepend
the relative path when it was needed.
Adds support for .gitignore files to git_status_foreach() and
git_status_file(). This includes refactoring the gitattributes
code to share logic where possible. The GIT_STATUS_IGNORED flag
will now be passed in for files that are ignored (provided they
are not already in the index or the head of repo).
