lib/repo-refs: Allow resolving local collection-refs

Currently for a "normal" refspec you can choose to use
ostree_repo_resolve_rev_ext() instead of ostree_repo_resolve_rev() if
you only want to look at local refs (in refs/heads/) not remote ones.
This commit provides the analogous functionality for
ostree_repo_resolve_collection_ref() by adding a flag
OSTREE_REPO_RESOLVE_REV_EXT_LOCAL_ONLY and implementing it. This
will be used by Flatpak.

Closes: #1825
Approved by: jlebon

src/libostree/ostree-repo.h

@@ -465,9 +465,11 @@ gboolean      ostree_repo_resolve_rev (OstreeRepo  *self,
 /**
  * OstreeRepoResolveRevExtFlags:
  * @OSTREE_REPO_RESOLVE_REV_EXT_NONE: No flags.
+ * @OSTREE_REPO_RESOLVE_REV_EXT_LOCAL_ONLY: Exclude remote and mirrored refs. Since: 2019.2
  */
 typedef enum {
   OSTREE_REPO_RESOLVE_REV_EXT_NONE = 0,
+  OSTREE_REPO_RESOLVE_REV_EXT_LOCAL_ONLY = (1 << 0),
 } OstreeRepoResolveRevExtFlags;
 
 _OSTREE_PUBLIC