Tracker task for epoch-related issues that need solving in eopkg

[ermo]

• Eopkg needs to be tested to ensure that it can handle moving from the various baselayout states post usr-merge script to a new baselayout with corrected merged paths in it (IE, are we sure it won't do something stupid like try to delete the /bin symlink) - Essential
• Eopkg needs to be able to transparently move between eopkg.py2 and eopkg.py3, whilst having its LazyDB caches and its FilesDB cache regenerated on demand.
  • py2 LazyDB/FilesDB: Use pickle protocol v2, write gdbm-backed shelve, set FILESDB_FORMAT_VERSION = 3 #86
  • eopkg.py3: eopkg.py2 LazyDB and FilesDB compat tweaks #89
• Eopkg needs to detect the marker file in order to move to a new repo - Essential
• Eopkg needs to be modified so it operates on /usr before any other paths and special-case handles /bin//sbin//lib//lib64/lib32 and skips files if the equivalent file exists under /usr - Optional but highly recommended
  • This would solve the entire eopkg check thing, as well as ensuring that eopkg doesn't do anything stupid