Merge with Patrick improvement

obsolete: do not obsolete rebase --detach nullmerge revs Rebase state contains the changesets to rebase as well as 'nullmerge' entries used drive the merge strategy. These nullmerge were not rebased and should be ignored, and certainly not be marked obsolete.

evolve: fix relocate() with removed revision relocate() was not handling the case where the rebased revision was discarded and was raising when trying to update the phase of None.

test-obsolete-rebase.t: test --abort and --continue

obsolete: handle rebase --collapse Recording obsolete in concludenode() did not work for --collapse because only the first revision was passed to the call. The new strategy is to track the rebase state in defineparents() and concludenode() and to create markers only after a successful non-abort call. In theory, this should also fix --continue/--abort cases. The change in test-stabilize-order.t comes from concludenode() no longer creating obsolete marker. stabilize command was actually duplicating markers, once in concludenode(), once explicitely.

test-stabilize-order.t: trace obsolete markers Will prevent breakage in rebase.concludenode() overriding.

test-obsolete-rebase.t: move --keep test from test-obsolete.t

obsolete: handle rebase removing empty changesets The new revision identifier returned by concludenode() was None and was not correctly translated to nullid.

obsolete: add or fix debug commands help

obsolete: do not duplicate command help