tests: correct the remaining fallout from recent path style changes on Windows Per @martinvonz, `ui.slash` set by the test runner is now capable of playing a more active role.[1] I verified that both of these work by setting `ui.slash` to False, but these changes seem cleaner. The problem with check-perf-code.py was that the proper imports were not being whitelisted due to '\' vs '/'. [1] https://www.mercurial-scm.org/pipermail/mercurial-devel/2019-February/128701.html

templates: adding a config() function for template customization This allows templates to be written such that users can customize them easily, or that they can be customized based on other configuration of the system. For enterprise deployments, we often have complex template aliases, and right now the only way individual users can customize those is by replacing the whole template alias (which means they won't get company-wide updates to it anymore, plus most users don't want to have to get a complex template right). With this change, they can just set a config option which feeds into our templates for common changes (e.g. whether to limit commit descriptions to the width of their terminal or not). To work around the issue of having to register the config options, I declared a dedicated section [templateconfig] for these options to be dynamically declared. They can still reference any other config option that's registered elsewhere. I only did string, bool and int at this time - list and date would add other complications with parsing the default so I'll leave that as an exercise to the reader :) Differential Revision: https://phab.mercurial-scm.org/D5959

changegroup: don't try to prune manifest nodes if not ellipses In non-ellipses case, the number of manifest nodes can be very big, and finding whether one of them can be pruned or not is very costly. For each node, we try to find the rev and the linkrev, which is expensive. Sending bit more manifest nodes seems better and much faster here. On our internal repository, this saves around 5 seconds on `hg tracked --addinclude <some_path>` on a narrow repo with ellipses disabled. Differential Revision: https://phab.mercurial-scm.org/D5782