rebase: fix working copy location after a --collapse (issue4080) Rebasing with --collapse would leave the working copy on the parent of the collapsed commit, instead of on the collapsed commit. This fixes that. Also fixes a few tests that already covered this area but had bad data. This also fixes issue3716 where bookmarks are not kept across rebases with --collapse. I updated the test to cover that case as well.

Merge with stable.

rebase: fix rebase aborts when 'tip-1' is public (issue4082) When aborting a rebase where tip-1 is public, rebase would fail to undo the merge state. This caused unexpected dirstate parents and also caused unshelve to become unabortable (since it uses rebase under the hood). The problem was that rebase uses -2 as a marker rev, and when it checked for immutableness during the abort, -2 got resolved to the second to last entry in the phase cache. Adds a test for the fix. Add exception to phase code to prevent this in the future.