tests: add a test file of resolving orphaness of merge changesets This patch adds a new test file named test-evolve-orphan-merge.t which contains test cases when `hg evolve` try to stabilize a merge changeset which was orphan. This file contains 20-30% of all the cases as we have got something to fix before we add tests for rest of the cases. Going by this approach will make sure we don't live unfixed cases in the test file and the test files does not become a pile of hacks which are used to get in state when we fix the bugs.

grab: gracefully handle the case when we try to grab parent of wdir Before this patch, we go all the way down to obsmarker creation logic and gets an error saying that changeset cannot obsolete itself. We should be more smart here and error out early saying we cannot grab that changeset.

grab: move the initialization of pctx variable outside of if-else The pctx variable is used outside of the if-else but it was initialized under the conditional statements. Added test for the case when the initialization inside the if-else broke `hg grab --continue`.

compat: drop hack around http request handling for 4.6 The approach we used in 4.5 works again :-)

obsdiscovery: add compatibility layer to register wireproto command Mercurial core 0b18604db95e changed the way permissions are registered.

compat: pass all hgweb dispatch argument to the orig function This make use compatible with whatever changes on this side.

grab: add short version for continue and abort

obsdiscovery: include units in ui.progress() calls (issue5773)