Wrap the skip-subtree feature
Make this less surprising
Repository#include?: support short SHA1s
Add methods to make using Rugged::Diff#stat more user friendly.
Remove `Rugged::Diff#tree` and `Rugged::Diff#owner`.

Fixes #389.
Merge pull request #392 from libgit2/arthur/remove-diff-owner

Remove `Rugged::Diff#tree` and `Rugged::Diff#owner`.
Remove defunct `Rugged::Diff::Line#hunk` and `Rugged::Diff::Line#owner`.

Fixes #390.
Merge pull request #393 from libgit2/arthur/remove-diff-line-owner

Remove defunct `Rugged::Diff::Line#hunk` and `Rugged::Diff::Line#owner`.
Make `Rugged::Diff` reference their repository.

We need to keep a reference from the diff objects to the repository to
ensure that the underlying libgit2 data does not get freed accidentally.
Add rb_git_remote_check_connection

This is useful if one needs to check if it is possible to
fetch/push from/to the remote.

Basically this is the analogue to `git fetch --dry-run` and `git push
--dry-run`.
Merge pull request #397 from dmedvinsky/remote-check-connection

Add rb_git_remote_check_connection
Implement `Repository#expand_oids`
Merge pull request #394 from libgit2/arthur/diff-should-keep-repository

Make `Rugged::Diff` reference their repository.
Merge pull request #398 from libgit2/vmg/expand-objects

Implement `Repository#expand_oids`
rename head_orphan? -> head_unborn? into README.md
Merge pull request #399 from daisuko/fix-rename-method-into-readme

update README
Bump libgit2 to 59403f1ff55346c64bfaa0744ea7f3375da71725
Type check the tree value for Rugged::Index#read_tree

libgit2 does no type checking in `git_index_read_tree` which means that
`index.read_tree` will segfault if you pass something other than a tree.

This ensures that the value passed is actually a tree.
Tabs not spaces
Merge pull request #401 from libgit2/type-check-read-tree

Type check the tree value for Rugged::Index#read_tree