tests: make run-tests exit non-zero if there are "errors" Previously, if there was an error such as a broken .t file that caused run-tests.py to encounter an exception during parsing, the test would be considered in an "errored" state, which is separate from "failed". The check for whether to exit non-zero or not was based entirely on whether there were any tests in a "failed" state, so if there was only an error, run-tests would exit with 0. Our test infrastructure would then consider the test as passing, causing us to have some tests with false negatives that have gone undetected for a few weeks now. Differential Revision: https://phab.mercurial-scm.org/D6452

perf: add a `perfhelper-mergecopies` command This command gather data that are useful to pick argument for `perfmergecopies`.

perf: add a new `perfmergecopies` command This command benchmark calls to `mercurial.copies.mergecopies`

perf: factor selection of revisions involved in the merge out We will introduce more performance command around merge. As a first step we factor out pieces of `perfmergecalculate` that can be reused.

perf: allow to specify the base of the merge in perfmergecalculate We can now test the rebase case.

perf: add a --from flag to perfmergecalculate Before this change, `perfmergecalculate` was always benchmarking the merge of the working copy with another revision. We can now benchmark the `mergecalculate` call for any arbitrary pair of revision.

merge with stable

py3: fix test-narrow* which started failing because of recent changes #skip-blame because just r'' prefix Differential Revision: https://phab.mercurial-scm.org/D6447