changegroup: pass sorted revisions into group() (API) Currently, group() receives a list of nodes and calls _sortgroup() to sort them and turn them into revs. Since the sorting behavior varies depending on the type of data being transferred, I think it makes sense to perform the sorting before group() is invoked. This commit extracts _sortgroup() to a pair of standalone functions. It then moves the calling of these functions to the 3 call sites of group(). group() now receives an iterable of revs instead of nodes. Differential Revision: https://phab.mercurial-scm.org/D4139