Add/Fetch NSData from index

[sagmor]

Hi,

I added support for libgit2 git_index_add_frombuffer function on GTIndex with the following methods:

// - (NSData *)dataWithName:(NSString *)name error:(NSError **)error; (removed)
- (BOOL)addData:(NSData *)data withName:(NSString *)name error:(NSError **)error;

I still have to add some documentation and need to make it work with an inMemoryIndexWithRepository:error:

Also I had to update External/libgit2 to get the method, not sure if there's an issue with this.
Right now GTIndexSpec is passing but have failing specs at GTConfigurationSpec and GTRemoteSpec

So, I'm still working on it but I'm pushing this in case you find something fishy (specially with the updated dependency and the two failing specs)

[sagmor]

I think I will move the data fetching to GTIndexEntry to make it work more like GTTreeEntry for API consistency.

[sagmor]

Now this is working better.

The only problem I'm having is that this doesn't work with in memory indexes because git_index_add_frombuffer fetches the repository from the struct's rc.owner property which looks like it can't be set without touching libgit2.

Let me know if you see any issue with this PR 👍

[joshaber]

Looks like these can't be nil according to the implementation. Could we document that?

[joshaber]

Awesome, thanks! 🍻

The only problem I'm having is that this doesn't work with in memory indexes because git_index_add_frombuffer fetches the repository from the struct's rc.owner property which looks like it can't be set without touching libgit2.

No worries. Just a couple other notes.

[sagmor]

There it is 😄

I addressed those notes and a couple more I found around

[joshaber]

🤘

Thanks!

[sagmor]

Cool 👍