lib/core: Add ostree_validate_remote_name() for remote names

There are a few places in the code where ad-hoc validation was being
performed. Might as well formalise it a bit more.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

Closes: #948
Approved by: cgwalters

src/libostree/ostree-core.h

@@ -242,6 +242,9 @@ int ostree_cmp_checksum_bytes (const guchar *a, const guchar *b);
 _OSTREE_PUBLIC
 gboolean ostree_validate_rev (const char *rev, GError **error);
 
+_OSTREE_PUBLIC
+gboolean ostree_validate_remote_name (const char *remote_name, GError **error);
+
 _OSTREE_PUBLIC
 gboolean ostree_parse_refspec (const char *refspec,
                                char      **out_remote,