largefiles: eliminate an unnecessary import of configitems Thanks to Yuya for pointing this out.

exthelper: add some examples for using registrar aliases Maybe it's my general lack of python knowledge, but how to use these would be way too obscure for me otherwise.

exthelper: reintroduce the ability to register filesets Same mechanism as revsets earlier in this series. The LFS extension is updated to provide test coverage.

exthelper: reintroduce the ability to register templates Same mechanism as revsets earlier in this series. The LFS extension is updated to provide test coverage. This also seems to make the test failure around issue6033 mentioned in 0a7f582f6f1f much less regular on Windows.

extensions: deprecate extsetup without a `ui` argument (API) 9.5 years should be enough time, but there were some tests for the old style still (which are now updated). Exthelper doesn't fallback to the old API, so this is for consistency. .. api:: The extension hook ``extsetup`` without a `ui` argument has been deprecated, and will be removed in the next version. Add a `ui` argument to avoid the deprecation warning.

largefiles: port revset registration to exthelper This tests the merge code that wasn't tested in the previous patch.

exthelper: reintroduce the ability to register revsets I think this is what Yuya and Boris agreed on.[1] This happens *after* the extsetup phase now (and after the _aftercallback notifications). But this is trivial, mergeable between exthelper instances, and doesn't need to have the extension name supplied when registering. The test needed updating so that extsetup() takes a `ui` argument, as exthelper isn't trying to be backward compatible with 1.3.1. [1] https://www.mercurial-scm.org/pipermail/mercurial-devel/2018-December/125888.html

largefiles: drop the uisetup module This is small enough to live in the __init__ module.

branches: add -r option to show branch name(s) of a given rev (issue5948) Differential Revision: https://phab.mercurial-scm.org/D5486

progress: avoid ui.configbool() lookup when progress bar is active Profiling revealed that the ui.configbool('progress', 'debug') during progress bar updates was consuming a significant amount of overhead. This commit adds an attribute on progress bar instances that caches this config option. The impact on `hg perfprogress` with default options is significant: before: ! wall 4.641942 comb 4.580000 user 4.210000 sys 0.370000 (best of 3) after: ! wall 1.948626 comb 1.950000 user 1.950000 sys 0.000000 (best of 5) After this change, profiling reveals that progress.progbar.progress() is now consuming ~73% of time. This change does not improve the execution time if the progress bar is disabled. We may want a more comprehensive solution for that case, as the progress bar won't be enabled in a number of scenarios (e.g. servers and processes not attached to an interactive TTY). I also think that overhead of ~2.0s for 1M updates is a bit high. I suspect further refactoring of the progress bar can significantly reduce overhead. I don't have plans to do this, however. Differential Revision: https://phab.mercurial-scm.org/D5408