topic: check availability of obsutil.getmarkers() for portability Before this patch, topic extension causes unintentional failure with Mercurial earlier than 4.3, because obsutil.getmarkers() has been available since Mercurial 4.3 (tests for topic on mercurial-4.* branches fail, too). This breaks "minimumhgversion = '4.0'" declaration of topic extension. This patch fixes this issue in a straightforward way for simplicity on stable branch. I'm planning to centralize such portability logic in topic extension into topic/compat.py or so on default branch for efficiency at runtime, like as evolve/compat.py.

tests: add more explicit test about empty topic from publishing

convertbookmark: advertise the new command in the readme The command is in a good enough shape now.

convertbookmark: properly convert stacked bookmarks We ignores pure descendant when looking for revision to convert. This adds support for cases were a linear stack contains multiple bookmark (or un-bookmarked descendants exists). In this case, some changeset are left orphan, but we'll consider the issue as minor for now.

convertbookmark: perform all actions at the end This will make the whole operation more deterministic and robust.

converbookmark: split target computation from actual update This will allow for further refactoring helping consistency.

convertbookmark: extract the revset into a module level constant This will make it easier to read and modify the query.

convertbookmark: properly exclude public changeset Public changeset are immutable and cannot have a topic anyway.

test: add a new root changeset to all debugconvertbookmark test case We'll make this root changeset public to check the debugconvertbookmark logic in that regards. It is added in its own changeset since it massively impact all output.

tests: import section in 'test-topic-debugcb.t' We now have two levels of titles to clarify some aspect of the tests.

test: avoid using debugdrawdag in 'test-topic-debugcb.t' The 'debugdrawdag' utility adds local tags that prevent hidden changeset to get hidden. We will do without that extension for now.

tests: add more tests for debugconvertbookmark

convertbookmark: add logic to skip revisions with multiple bookmarks When a user tries to converts a bookmark to topic which is on a changeset with more bookmarks we skip that.

topics: add a new debugconvertbookmark command to convert bookmarks to topics This new command, aliased to debugcb converts bookmarks to topics. This command either accept name of a bookmark using flag '-b' or '--all'. If a bookmark is passed using '-b', the whole stack defined by that bookmark is converted to topics. If '--all' is passed, the above thing is repeated for every bookmark in the repository. If the revset which we are using unable to decides revisions of the stack and return an expty set, in that cases we are not deleting the bookmark as we are not writing any topics of the same name as that of bookmark. Also currently if a changeset has two bookmarks, than there is buggy behaviour. So these are known lackings in the current implementation which will be fixed in upcoming patches. This also adds tests for the same.