changelog: extract a _string_unescape() to mirror _string_escape() We use our own _string_escape() to encode the "extras" field. Then we use codecs.escape_decode() to escape it. But there's also a little workaround for dealing with escaped text that looks like octal numbers since the fix for https://bz.mercurial-scm.org/show_bug.cgi?id=3156. This patch extracts the call to codecs.escape_decode() along with the fix for octal numbers and puts it in a _string_unescape(). It also updates the test to check for the octal-number case from the aforementioned bug. As you may have suspected, I want to be able to reuse this new function later. Differential Revision: https://phab.mercurial-scm.org/D6184

copies: extract function for deciding whether to use changeset-centric algos We'll eventually have a "experimental.copies.read-from=changeset-only" option too and I don't want to spread the logic for determining if we should use changeset-centric of filelog-centric algorithms. Differential Revision: https://phab.mercurial-scm.org/D6163

getrenamedfn: get copy data from context object if configured The function returned from getrenamedfn() calls filelog.renamed(). That won't work when storing copy metadata in the changeset. I've just switched to a simple implementation here. We may or may not need to optimize it later, possibly by optimizing the callers. No more tests fail with "--extra-config-opt experimental.copies.read-from=compatibility)" than they did before this patch. Differential Revision: https://phab.mercurial-scm.org/D6162

branchmap: implement __contains__() We have good occurences of `if branch in branchmap()` in our code. If __contains__() is not implemented then it will use __iter__() to find whether the element exists or not which is not good. I am bit confused that whether I should move existing callers to hasbranch() or this patch is a good way. Differential Revision: https://phab.mercurial-scm.org/D6206

branchmap: prevent using __getitem__() in branchheads() branchheads() can directly use self._entries instead. Differential Revision: https://phab.mercurial-scm.org/D6205

branchmap: dynamically resolve type of branchcache class This is required to support subclassing. Thanks to Yuya for suggesting this in D6151. Differential Revision: https://phab.mercurial-scm.org/D6204

copies: print list of divergent renames in sorted order The current order is not obvious to the user (and I may change it in a later patch). Lexicographical order seems like the obvious choice here. Differential Revision: https://phab.mercurial-scm.org/D6227

import: suppress accept: header irccloud and others may perform content negotation and reject (406) if the accept header does not match the mime type of the object

rebase: fix bug that prevented dry-run rebases from printing failures As far as I can tell it should be fine to unconditionally skip _prepareabortorcontinue if we're in the process of raising an Abort here. Differential Revision: https://phab.mercurial-scm.org/D6226

rebase: demonstrate bug in dry-run mode which causes cycles to not be reported Differential Revision: https://phab.mercurial-scm.org/D6225