merge: rework iteration over mergeresult object in checkpathconflicts() Instead of following pattern: ``` for f, (m, args, msg) in mresult.actions.items(): if m == mergestatemod.ACTION_*: ... elif m == mergestatemod.ACTION_*: ... .... ``` We do: ``` for (f, args, msg) in mresult.getaction((mergestatemod.ACTION_*,)): ... for (f, args, msg) in mresult.getaction((mergestatemod.ACTION_*,)): ... .... ``` This makes code bit easier to understand and prevent iterating over actions which we don't need. Differential Revision: https://phab.mercurial-scm.org/D8884