Change getattr and statx to bespoke policies

* Provides: slight improvement in performance as it no longer will
need to find and then act on the files.
* It doesn't make sense to support all original policy types. Most
people used 'newest' or 'ff' and 'combine' is a better default which
has same runtime as 'newest' but with better output.

src/func_listxattr_ff.cpp

@@ -0,0 +1,53 @@
+#include "func_listxattr_ff.hpp"
+
+#include "error.hpp"
+#include "fs_llistxattr.hpp"
+
+
+std::string_view
+Func2::ListxattrFF::name() const
+{
+  return "ff";
+}
+
+static
+ssize_t
+_listxattr_ff(const Branches &branches_,
+              const fs::path &fusepath_,
+              char           *list_,
+              const size_t    size_)
+{
+  Err err;
+  ssize_t rv;
+  fs::path fullpath;
+
+  for(const auto &branch : branches_)
+    {
+      fullpath = branch.path / fusepath_;
+
+      rv = fs::llistxattr(fullpath,list_,size_);
+      switch(rv)
+        {
+        case -ERANGE:
+        case -ENOTSUP:
+        case -E2BIG:
+          return rv;
+        default:
+          if(rv >= 0)
+            return rv;
+          err = rv;
+          break;
+        }
+    }
+
+  return err;
+}
+
+ssize_t
+Func2::ListxattrFF::operator()(const Branches &branches_,
+                               const fs::path &fusepath_,
+                               char           *list_,
+                               const size_t    size_)
+{
+  return ::_listxattr_ff(branches_,fusepath_,list_,size_);
+}