tests: add a critical flush() to run-tests.py to make output stable on py3 Differential Revision: https://phab.mercurial-scm.org/D5204

merge-tools: when calling external merge tool, describe the resolve inputs It is a common complaint that a user will be running some operation (histedit, rebase, evolve, etc.), get into a merge-conflict situation, and not understand what they are seeing - it is possible that the merge tool is configured to display the hash, but it's difficult for most merge tools to display a good snippet of the description. In the worst case, configuring this template will lead to output that is immediately covered by a terminal application, maybe the user can hit ctrl-z to see it. In the common case, the output will be in a terminal window and a GUI program will start, and it should be possible to view both the terminal and the GUI program at the same time. Differential Revision: https://phab.mercurial-scm.org/D5094

templatekw: deprecate p1rev/p2rev/p1node/p2node in favor of p1/p2

templatekw: add p1/p2 keywords which switches the current ctx This is just an example of mappingdict. I have no idea what should be displayed as {p1|json}. Currently it is an empty dict since {'ctx'} isn't displayable, which is clearly useless and should be changed later.

templater: add wrapper for a single template mapping This can be used to nest template mappings without inserting a sequence-like layer. See the next patch for example.

templatekw: extract internal "{rev}:{node|formatnode}" template to constant This will be used later.

tweakdefaults: remove commands.resolve.mark-check=abort, it is too broken See issue6020 for the current case. I don't want to continue attempting to fix this on the stable branch, so I'm removing from tweakdefaults and will send fixes meant for the default branch and 4.9. Differential Revision: https://phab.mercurial-scm.org/D5225

resolve: when resolve.mark-check=abort, downgrade to warning if pats specified Previously, with --config resolve.mark-check=abort, running `hg resolve -m foo` would abort and emit a message saying to use --all. This command does not work, though: `hg resolve -m foo --all`, and it's really weird for --all to be the "--force" flag. My original goal with the option was to make it so that `hg resolve -m` (no filename arguments) was safer, which is why --all is used; in my mind, `hg resolve -m foo` should always mark it as resolved, and `--all` is how you specify "all the files", so that's why I chose `hg resolve -m --all` as the way out of `hg resolve -m` aborting. This commit makes all of this work the way it was meant to in my head :) Differential Revision: https://phab.mercurial-scm.org/D5218

test: remove changes preparing the drop of `HGMERGE` These changes are no longer necessary so we better drop them.

run-tests: define the default merge tool through configuration Using the `HGMERGE` environment variable generates confusion as it overrides any value set through configuration. By setting the default value through the default HGRC, the usual overriding rules apply and it should reduce confusion.