repository: Change ownership semantics

The ownership semantics have been changed all over the library to be
consistent. There are no more "borrowed" or duplicated references.

Main changes:

	- `git_repository_open2` and `3` have been dropped.

	- Added setters and getters to hotswap all the repository owned
	objects:

		`git_repository_index`
		`git_repository_set_index`
		`git_repository_odb`
		`git_repository_set_odb`
		`git_repository_config`
		`git_repository_set_config`
		`git_repository_workdir`
		`git_repository_set_workdir`

	Now working directories/index files/ODBs and so on can be
	hot-swapped after creating a repository and between operations.

	- All these objects now have proper ownership semantics with
	refcounting: they all require freeing after they are no longer
	needed (the repository always keeps its internal reference).

	- Repository open and initialization has been updated to keep in
	mind the configuration files. Bare repositories are now always
	detected, and a default config file is created on init.

	- All the tests affected by these changes have been dropped from the
	old test suite and ported to the new one.

1 files changed, 13 insertions, 6 deletions

diff --git a/src/refs.c b/src/refs.c
index 2374cc72f..4c45fec2c 100644
--- a/src/refs.c
+++ b/src/refs.c
@@ -1195,7 +1195,8 @@ cleanup:
  */
 int git_reference_set_oid(git_reference *ref, const git_oid *id)
 {
-	int error = GIT_SUCCESS;
+	int error = GIT_SUCCESS, exists;
+	git_odb *odb = NULL;
 
 	if ((ref->flags & GIT_REF_OID) == 0)
 		return git__throw(GIT_EINVALIDREFSTATE,
@@ -1203,23 +1204,29 @@ int git_reference_set_oid(git_reference *ref, const git_oid *id)
 
 	assert(ref->owner);
 
+	error = git_repository_odb__weakptr(&odb, ref->owner);
+	if (error < GIT_SUCCESS)
+		return error;
+
+	exists = git_odb_exists(odb, id);
+
+	git_odb_free(odb);
+
 	/* Don't let the user create references to OIDs that
 	 * don't exist in the ODB */
-	if (!git_odb_exists(git_repository_database(ref->owner), id))
+	if (!exists)
 		return git__throw(GIT_ENOTFOUND,
 			"Failed to set OID target of reference. OID doesn't exist in ODB");
 
 	/* Update the OID value on `ref` */
 	git_oid_cpy(&ref->target.oid, id);
 
+	/* Write back to disk */
 	error = loose_write(ref);
 	if (error < GIT_SUCCESS)
-		goto cleanup;
+		return git__rethrow(error, "Failed to set OID target of reference");
 
 	return GIT_SUCCESS;
-
-cleanup:
-	return git__rethrow(error, "Failed to set OID target of reference");
 }
 
 /*