submodule: add newline on invalid submodule error

Since 'err' contains output for multiple submodules and is printed all
at once by fetch_populated_submodules(), errors for each submodule
should be newline separated for readability. The same strbuf is added to
with a newline in the other half of the conditional where this error is
detected, so make the two consistent.

Signed-off-by: Emily Shaffer <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: nasamuffin

submodule.c

@@ -1478,7 +1478,7 @@ static int get_next_submodule(struct child_process *cp,
 			    !is_empty_dir(ce->name)) {
 				spf->result = 1;
 				strbuf_addf(err,
-					    _("Could not access submodule '%s'"),
+					    _("Could not access submodule '%s'\n"),
 					    ce->name);
 			}
 		}