Merge branch 'ds/midx-normalize-pathname-before-comparison' into maint

The path taken by "git multi-pack-index" command from the end user was compared with path internally prepared by the tool withut first normalizing, which lead to duplicated paths not being noticed, which has been corrected. source: <pull.1221.v2.git.1650911234.gitgitgadget@gmail.com> * ds/midx-normalize-pathname-before-comparison: cache: use const char * for get_object_directory() multi-pack-index: use --object-dir real path midx: use real paths in lookup_multi_pack_index()