copies: mark checkcopies as internal with the _ prefix

copies: split u1/u2 to u1u/u2u and u1r/u2r These will be made different in case of grafts by another patch in this series.

copies: style fixes and add comment

copies: limit is an optimization, and doesn't provide guarantees

revset: do not rewrite ':y' to '0:y' (issue5385) That's no longer valid since the revision 0 may be hidden. Bypass validating the existence of '0' and filter it by spanset.

revset: extract function that creates range set from computed revisions So we can pass m=0 to _makerangeset() even if the revision 0 is hidden. Hidden revisions are filtered by spanset.

lazymanifest: write a more efficient, pypy friendly version of lazymanifest

hg: set default path correctly when doing a clone+share (issue5378) Before, if performing a clone+share from a repo that was itself using shared storage, the share code would copy paths.default from the underlying repo being shared, not from the source given by the user. This patch teaches hg.clonewithshare to resolve paths.default and pass it to share so it can be written to the hgrc accordingly.

annotate: calculate line count correctly Before this patch, the "lines" function inside "annotate" returns 1 for empty text (''). This patch makes it 0. Because the function should match mdiff.splitnewlines (used by mdiff.allblocks), or s.splitlines (used at the end of the "annotate" method). Both len(mdiff.splitnewlines('')) and len(''.splitlines(True)) are 0. This issue was discovered while testing fastannotate [1]. I could not find a test case to reveal this issue. However in theory this could reduce memory usage a little bit, and avoids surprises when people are touching this area in the future. [1]: https://bitbucket.org/facebook/hg-experimental/commits/525b3b98e93a

py3: use unicode in is_frozen() imp.is_frozen() doesnot accepts bytes on Python 3. It does accept both bytes and strings on Python 2.