histedit: add --edit-plan option to histedit --edit-plan allows user to edit remaining histedit rules in the middle of histedit process

histedit: generalize makedesc Allow makedesc to generate description for any action - not only pick. (to be used in histedit --edit-plan)

histedit: extract method ruleeditor Extract functionality of editing histedit rules to separate method so we can reuse it in upcoming --edit-plan option.

churn: deprecate -t option in favour of -T We use -T consistently elsewhere to refer to the --template option. The old -t option is now renamed to --oldtemplate so that -t still works. This has the benign side effect of introducing and immediately deprecating a new long option. We also test with both -t and -T options.

pull: print "pulling from foo" before accessing the other repo 1. This is consistent with pushing. 2. This allows to see the URL of the other repo in case accessing the repo fails, e.g. wrong ssh path or issues with the https certificate, without using --debug or showconfig paths. Additionally add test for this in the context of ssh with a wrong path.

error.LookupError: rename 'message' property to something else At least some installs of Python 2.6+ complain with: mercurial/error.py:26: DeprecationWarning: BaseException.message has been deprecated as of Python 2.6 This patch renames the property away from 'message' so that Python no longer complains.