mergeresult: yield from getactions() instead of buidling a list and returning Only 7 out of 29 callers change the underlying dict while iterating. So it's better to yield and wrap the 7 callers with `list()`. Differential Revision: https://phab.mercurial-scm.org/D8882

sparse: replace merge action values with mergestate.ACTION_* constants Having bytestrings like `b'r'` makes it hard to understand for people who don't know the code much or looking at it for the first time. Differential Revision: https://phab.mercurial-scm.org/D8881