merge: ensure that we always commit the mergestate In future patches, we may halt the merge process based on configuration or user requests by raising exceptions. We need to ensure that the mergestate is unconditionally committed even when such an exception is raised. Depends on D930. Differential Revision: https://phab.mercurial-scm.org/D931

merge: add tests to show current behavior on failed filemerges Currently, failed file merges will nevertheless force the user to continue attempting to merge all additional unresolved files. Future patches will allow the user to halt the merge process instead. This patch first introduces a test demonstrating the current bejhavior so the upcoming changes are more obvious. Differential Revision: https://phab.mercurial-scm.org/D930

dirstate: move the _dirfoldmap to dirstatemap Now that dirstatemap is the source of truth for the list of directories, let's move _dirfoldmap on to it. This pattern of moving cached variables onto the dirstate map makes it easier to invalidate them, as seen by how the cache invalidation functions are slowly shrinking to just be recreating the dirstatemap instance. Differential Revision: https://phab.mercurial-scm.org/D983