When the glob iterator is passed NULL regexp, call the non-globbing
iterator so we don't have to special-case which functions to call.

Use a glob iterator instead of going through
git_config_backend_foreach_match. This function is left as it's
exposed in the API.

As the name suggests, it iterates over all the entries

Make it look like the refs iterator API.

Implement the foreach version as a wrapper around the iterator.

Like we have in the references iterator, next and free belong in the
iterator itself.

The plain function will return an iterator, so move this one out of
the way.

Really report an error in foreach if we fail to allocate the iterator,
and don't fail if the config is emtpy.

Make the iterator structure opaque and make sure it compiles.

new functions in struct git_config_backend:
  * iterator_new(...)
  * iterator_free(...)
  * next(...)

The old callback based foreach style can still be used with `git_config_backend_foreach_match`

This step is needed to easily add iterators to git_config_backend
As well use these new git_strmap functions to implement foreach

* git_strmap_iter
* git_strmap_has_data(...)
* git_strmap_begin(...)
* git_strmap_end(...)
* git_strmap_next(...)

Parse config headers with quoted quotes

Parse config headers that have the last quote on the
line quoted instead of walking off the end.

More tests for ambiguous OIDs across packs

The test coverage for ambiguous OIDs was pretty thin.  This adds
a bunch of new objects both in packs, across packs, and loose that
match to 8 characters so that we can test various cases of
ambiguous lookups.

submodule: check alloc and name presence

Fixes #1762

Allow Makefile.embed to be used when cross-compiling

This option is already present in the CMake config, but was missing from `Makefile.embed` and would cause all kinds of weird failures when compiling rugged on windows with the ruby devkit.

Fix possible double close

Fix -n bug; default to all ancestors

Signed-off-by: Sven Strickroth <email@cs-ware.de>

Close p->mwf.fd only if necessary

This fixes a regression introduced in revision 9d2f841a.

Signed-off-by: Sven Strickroth <email@cs-ware.de>

This allows libgit2 to be cross-compiled (e.g. when building native rugged binaries for windows from Linux or OS X).

```
CROSS_COMPILE=i686-w64-mingw32 make -f Makefile.embed
```

Doc fixes

The description of what the function does hasn't been true for quite a
while. Change it to reflect the way it currently works.

While here, remove an even older comment about missing features that
have been implemented.

clang's docparser highlighted these.

Invalid refs on disk cause revwalk globbing to fail

The new tests don't always want to use the same fixture data as
the old ones so this makes it configurable on a per-test basis.