patch 7.4.2162
Problem:    Result of getcompletion('', 'sign') depends on previous
            completion.
Solution:   Call set_context_in_sign_cmd(). (Dominique Pelle)
diff --git a/src/evalfunc.c b/src/evalfunc.c
index dc0e630..3754534 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -4247,6 +4247,13 @@
 	xpc.xp_pattern_len = (int)STRLEN(xpc.xp_pattern);
     }
 #endif
+#ifdef FEAT_SIGNS
+    if (xpc.xp_context == EXPAND_SIGN)
+    {
+	set_context_in_sign_cmd(&xpc, xpc.xp_pattern);
+	xpc.xp_pattern_len = (int)STRLEN(xpc.xp_pattern);
+    }
+#endif
 
     pat = addstar(xpc.xp_pattern, xpc.xp_pattern_len, xpc.xp_context);
     if ((rettv_list_alloc(rettv) != FAIL) && (pat != NULL))