subrepo: add bailifchanged to centralize raising Abort if subrepo is dirty This patch also centralizes composing dirty reason message like "uncommitted changes in subrepository 'xxxx'".

subrepo: add dirtyreason to centralize composing dirty reason message This patch newly adds "dirtyreason()" to centralize composing dirty reason message like "uncommitted changes in subrepository 'xxxx'". There are 3 similar messages below, and this patch is a part of preparations for unifying them into (1), too. 1. uncommitted changes in subrepository 'XXXX' 2. uncommitted changes in subrepository XXXX 3. uncommitted changes in subrepo XXXX This patch chooses adding new method "dirtyreason()" instead of making "dirty()" return "reason string", because: - some of existing "dirty()" implementation is too complicated to do so simply, and - ill-mannered 3rd party subrepo classes, of which "dirty()" doesn't return "reason string", cause meaningless message (even though it is rare case)

record_curses: add test for newly added files We have a UI bug where toggling a newly added file twice in the curses interface didn't mark it as selected. This test checks that the underlying logic is working as expected, the next patch of the series fixes the UI bug.