tests: add test to show widening is broken without ellipsis This patch adds a test to show that widening a narrow clone is broken if ellipsis is disabled. I don't think I can add cases to existing test-narrow-widen.t and check-in a failing version of that. So I created a copy. Once the test is fixed, we can merge this new test file back into the original one using testcases. Also, this is just testing treemanifest case because having two cases and both or are failing with different outputs is a bit hard to manage. This is important because upcoming patches will try to fix the broken part. Differential Revision: https://phab.mercurial-scm.org/D4382

stringutil: emit multiple chunks when pretty printing This avoids concatenating output inside pprintgen() itself. But the real reason for this is it will make it easier to add indentation, as we'll need to account for indentation when emitting each individual object in a collection. The verbosity of this code compared to the original is a bit unfortunate. But I suppose this is the price to pay for having nice things (streaming and indenting). We could probably abstract the "print a collection" bits into a generic function to avoid some duplication. But I'm not overly inclined to do this. Differential Revision: https://phab.mercurial-scm.org/D4398

stringutil: refactor core of pprint so it emits chunks This commit splits the core of pprint() to a new function that is a generator of chunks instead of a function returning a single value. This will make it possible to stream output without waiting for all data to be formatted first. And it will make it easier to implement support for indenting. Differential Revision: https://phab.mercurial-scm.org/D4397

contrib: import the relnotes script from the release-tools repo I figure this makes more sense to keep in the main repo, as it's a guide of sorts on how to use the releasenotes extension in the presence of commits that don't get relnotes annotations. Ported to Python 3, cleaned up some logic in a few places, but for the most part it's what we've been using for years. Differential Revision: https://phab.mercurial-scm.org/D4291