Merge branch 'jk/config-warn-on-inaccessible-paths' into maint

The attribute system may be asked for a path that itself or its leading directories no longer exists in the working tree, and it is fine if we cannot open .gitattribute file in such a case. Failure to open per-directory .gitattributes with error status other than ENOENT and ENOTDIR should be diagnosed. * jk/config-warn-on-inaccessible-paths: attr: failure to open a .gitattributes file is OK with ENOTDIR warn_on_inaccessible(): a helper to warn on inaccessible paths attr: warn on inaccessible attribute files gitignore: report access errors of exclude files config: warn on inaccessible files