view CONTRIBUTING @ 38351:bec1212eceaa

progress: create helper class for incrementing progress

When using ui.progress(), there's a clear pattern that is followed:

 * Pass the same topic and unit
 * Usually pass the same total
 * Call with pos=None to close the progress bar
 * Often keep track of the current position and increment it

This patch creates a simple helper class for this. I'll probably make
it implement the context manager protocol later (calling update(None)
on __exit__).

Progress is used in low-level modules like changegroup, so I also
exposed it via a method on the ui object. Perhaps the class itself
should also live in ui.py?

This patch also makes merge.oy use it to show that it works.

Differential Revision: https://phab.mercurial-scm.org/D3765

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).