Add str methods to contexts

Add equality operators to changectx and filectx

localrepo.parents: return null context for no parents

Add localrepo.parents to get parent changectxs.

merge: move partial filtering out of manifest merge

merge: move findcopies after workingmanifest

findcopies: shortcut for empty working dir

fix users of dirstate.copies broken by b1f10d3223c1

Merge with crew

optimize revlog.lookup when passed hex(node)[:...] Instead of converting each node from the filenode to a hex form, convert the arg to a bin form. For a revlog with 26711 entries, doing 100 lookup: before: ~18s after : ~13s

cleanups in revlog.lookup - add comments - do a clean separation of the different cases - don't use a list of each possible node when doing the lookup, just keep the previous entry

findcopies: use dirstate rename information

dirstate: add copies function rename copies to copymap

Add core copy detection algorithm This adds findcopies, which detects merge-relevant copies between files in a pair of manifests back to the merge ancestor. While the merge code invokes the copy detection routine, it does not yet use the result.