annotate CONTRIBUTING @ 39899:f9232b0310ef

pullreport: issue a message about "extinct" pulled changesets

Changeset pulled from a remote repository while already obsolete locally can
end up hidden after the pull. Hiding obsolete changesets is a good behavior
but silently "skipping" some of the pulled content can get confusing.

We now detect this situation and emit a message about it. The message is
simple and the wording could be improved, however, we focus on the detection
here. Evolution is still an experimental feature, so the output is open to
changes.

In particular, we could point out at the latest successors of the obsolete
changesets, however, it can get tricky is there are many of them. So we delay
these improvements to another adventure.

Another easy improvement would be to merge this message with the previous line
about the new nodes and their phases.

This is a good example of cases where we can only transmit a limited amount of
data to users by default. We need some sort of "transaction journal" we could
point the user to.

Our full contribution guidelines are in our wiki, please see:

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
difficult on Windows), please at least run `contrib/check-code.py` on
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).