mergestate: move commit() from base class to on-disk subclass The commit message doesn't do anything in the in-memory case, and it's `_makerecords()` is also not needed in that case, so let's move it down to the on-disk subclass (i.e. the `mergestate` class). Sorry I missed this earlier. Differential Revision: https://phab.mercurial-scm.org/D9043

mergestate: make in-memory mergestate not clear on-disk mergestate on reset() Oops, I thought I had remove the `rmtree()` call earlier. Maybe I accidentally got it back in a histedit or something. Differential Revision: https://phab.mercurial-scm.org/D9042