mergestate: define NO_OP_ACTION in module scope instead of inside mergeresult This makes sure it isn't intended to be overridden by subclasses. Thanks to Yuya for the nice suggestion. Differential Revision: https://phab.mercurial-scm.org/D9025

mergestate: introduce a new ACTION_KEEP_NEW `ACTION_KEEP` is overloaded and it's hard to figure out how we end up with this KEEP, what was the state of things. In a previous patch, we introduced `ACTION_KEEP_ABSENT` which represents files which are kept absent in the working directory. There is another special case where we keep the file when it's not present on both ancestor and remote side. We introduce a dedicated action for that. The goal is to use these information to make bid merge smarter. Differential Revision: https://phab.mercurial-scm.org/D9002

repoview: don't crash if mergestate points to non-existent node Differential Revision: https://phab.mercurial-scm.org/D9078

tests: demonstrate crash caused by pinning of non-existent mergestate node If the mergestate somehow contains a reference to a non-existent node, it causes most commands to crash since aaeccdb6e654 (repoview: pin revisions for `local` and `other` when a merge is active, 2020-09-04). This patch adds a test showing that. Differential Revision: https://phab.mercurial-scm.org/D9077

git: also convert timezone to int (issue6359) Credit to moshez for testing this in the wild. Differential Revision: https://phab.mercurial-scm.org/D9062

chg: fallback to original hg if stdio fds are missing If stdio fds are missing (ex. fd 0 is not present), chg might open fds that take the numbers 0, and attachio would send the wrong fds to the client, which might cause unwanted behaviors. Avoid that by detecting the missing fds and falling back to the original hg. Differential Revision: https://phab.mercurial-scm.org/D9058