dispatch: take over SignalInterrupt handling from scmutil
dispatch handles KeyboardInterrupt already. This makes the code more
consistent, and makes worker not print "killed!" if it receives SIGTERM in
most cases (in rare cases there is still "killed!" printed, which will be
fixed by the next patch).
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https://www.mercurial-scm.org/wiki/ContributingChanges
If you just want a checklist to follow, you can go straight to
https://www.mercurial-scm.org/wiki/ContributingChanges#Submission_checklist
If you can't run the entire testsuite for some reason (it can be
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any files you've modified and run `python contrib/check-commit` on any
commits you've made (for example, `python contrib/check-commit
273ce12ad8f1` will report some style violations on a very old commit).