revsetlang: add utility function to return hash like symbols from the tree Functionalities like unhiding changesets whose rev/hash is passed by the user required the knowledge of rev/hashes in the user provided specs. This patch adds functions which can parse tree object and return a list of such values. Differential Revision: https://phab.mercurial-scm.org/D1732

repoview: add visibilityexception argument to filterrevs() and related fns After this patch, filterrevs() can take an optional argument visibilityexceptions which is a set of revs which should be exception to being hidden. The visibilityexceptions will be passed to the function computing hidden revisions for that filtername and are considered there while calculating the set of hidden revs. Differential Revision: https://phab.mercurial-scm.org/D1747

repoview: add visibilityexceptions as an optional argument to repo.filtered() This will help us in having an API where we can pass the filtername and the visibilityexceptions to get a new repo object. Visibility exceptions are the revs which must be visible even they should in theory belong to the hidden set. They are required as there has been desire to have a functionality to access hidden changesets using certain commands without passing --hidden. After this patch we can make those changesets visibility exceptions so that we can access them without requiring a unfiltered repo. Differential Revision: https://phab.mercurial-scm.org/D1746