rewriteutil: move disallowednewunstable in the new module

rewriteutil: create a rewriteutil module to host utility function The ultimate goal of this module is to gather basic building block for rewriting changesets. This is aimed at moving into core and being use by the core extension.

interactive: fix the interractive option import The move made in e6bc6eaa17c5 was buggy.

test: update test output to match b11e8c67fb0f hg debugobsolete now issues a message about the obsoleted changesets.

test: update test output from b47fef6d2365 We run this check for bundle1 too now.

compat: add a compatibility layer for bookmark move The API was updated in 4.3 (712a85b3677f) we adapt to that.

compat: use 'safehasattr' over 'hasattr' 'hasattr' is broken in python 2.

stack: show short node of changesets in `hg stack -v` After this patch, hg stack -v shows short nodes for changesets which have topic index, i.e. excluding the bases except t0.

compat: use 'repo.cachevfs' when available In 4133c0b0fcd7 (core), the repository gained a new vfs dedicated to caches. We update the code to follow this new pattern.

debugobsconvert: take the lock when writing the obsstore file We were upgrading the store unprotected.

topics: add a test demonstarting sorting of topics by time using --age

branching: merge with stable

prev: allow to update to 't0' from 't1' When on the first changeset of a topic, one can move back one changeset to end up on t0. The new working copy parent to not belong to the topic, but the topic is still active. The next commit will create a new root to the active topic. You can get the same result using `hg up t0`

topic: add a 'topicidx()' to context This will be useful for the `t0` logic in `hg prev`

prev: retrieve the 'no-topic' result is a clear and reusable option We'll use it more, so let us make it pretty first.