copyfile: add a option callback for failed hardlinking Local clone, adjust its UI depending on the success of using hardlinking, so we add a small callback making it possible for `copyfile` to signal if the requested hardlinking failed. Differential Revision: https://phab.mercurial-scm.org/D10853

streamingclone: extract the scanning part from the generation part We will reuse the scanning part for local clone, so we need it in a dedicated function. Differential Revision: https://phab.mercurial-scm.org/D10852

vfs: add a `register_file` method on the vfs class This is used by the fncache vfs to register new file. Until now, `fncache` have been doing this "automatically" by monitoring write pattern. However this is fragile and when we copy files in place by other means, we need something more robuts. So we add an explicit method to do so. Differential Revision: https://phab.mercurial-scm.org/D10851

clone: use "official" API to create local clone destination This make sure we have a properly created, fully functional repository early. This will be useful to simply the hardlink/copy phases of the local clone to make it share more of its logic with the similar "stream" cloning. This has a minor impact of the test and the resulting repository has is better initialized (eg: the `wcache` directory is pre-created.) Differential Revision: https://phab.mercurial-scm.org/D10850

localrepo: introduce a clone_requirements function This function take a source repository and return a relevant set of requirements that should be used by a copy clone. This will help make the creation of the destination repository during copy clone simpler. Differential Revision: https://phab.mercurial-scm.org/D10849

createrepository: allow to directly pass the target requirements This is useful when doing a local clone that copies store contents, it will requires the destination to use the very same store requirements so directly providing them will be simpler and safer Differential Revision: https://phab.mercurial-scm.org/D10848

narrowbundle: use new context manager for silencing the ui Same reasoning as the previous change. This affects a few tests because of the hack from d7304434390f (changegroup: move message about added changes to transaction summary, 2019-09-08). Differential Revision: https://phab.mercurial-scm.org/D10886

debugbackupbundle: use new context manager for silencing the ui A difference between setting `ui.quiet` and using `ui.silent()` is that the latter also silences `ui.write()` calls. That's practically always what one wants, including here, I think. Differential Revision: https://phab.mercurial-scm.org/D10885

ui: add a context manager for silencing the ui (pushbuffer+popbuffer) We often silence the ui by calling `ui.pushbuffer()` followed (a later in the code) by `ui.popbuffer()`. These places can be identified by the fact that they ignore the output returned from `ui.popbuffer()`. Let's create a context manager for these cases, to avoid repetition, and to avoid accidentally leaving the ui silent on exceptions. I deliberately called the new function `silent()` instead of `buffered()`, because it's just an implementation detail that it uses `pushbuffer()` and `popbuffer()`. We could later optimize it to not buffer the output. Differential Revision: https://phab.mercurial-scm.org/D10884

shelve: don't swallow errors that happen when reverting the working copy Same reasoning as the parent commit. The code in question here comes from fb8065de47b0 (unshelve: silence internal revert, 2014-08-15), which says that it was to prepare for some upcoming revert changes. I suppose those changes have happened by now but we fixed something about it, because I don't see any unwanted changes in tests (no changes at all in tests, in fact). Differential Revision: https://phab.mercurial-scm.org/D10883