Rework and fix HGSourceCodeManager >> #revisionLogOf:...directory:module:`
This commit changes the logic in two ways:
1. #newestRevision is now the newest revision in the branch that
*contains* given file (not necesarily modidfes it). If there are
multiple heads in that branch, pretty much random one is returned.
This changes old behavior and therefore this commit updates
tests.
2. If a specific single revision is requested, i.e., both from and to revisions
are the same, revision log with that single revision is returned
no matter whether it modifies the file or even contains that file
at all. This is essentially a workaround to fix issue #305.
Moreover, this commit simplifies the code a lot by delegating all the
changeset searching and filtering to mercurial using revset expressions.
See https://swing.fit.cvut.cz/projects/stx-jv/ticket/305#comment:3