byteify-string: resolve symlink before byteifying Otherwise the script turns symlinks into regular files.

tests: simplify test-fix-topology.t slightly by using a `(case !)` Differential Revision: https://phab.mercurial-scm.org/D8283

tests: fix rebase test broken by earlier cleanup It turns out I broke one of the rebase tests in dd2833e4d660 (tests: use drawdag in test-rebase-collapse.t, 2018-03-18) and didn't notice until now. Differential Revision: https://phab.mercurial-scm.org/D8277

rebase: accept multiple --base arguments (BC) Same reasoning as for the previous patch. Rebase has worked well with `--base 'A + B'` since 51e7c83e05ee (rebase: calculate ancestors for --base separately (issue5420), 2016-11-28). Differential Revision: https://phab.mercurial-scm.org/D8293

rebase: accept multiple --source arguments (BC) I think it's a little surprising that `hg rebase -s A -s B` rebases only `B::` and ignores `A`. That's because the `-s` flag is not a repeated flag. This patch makes it a repeated flag. Differential Revision: https://phab.mercurial-scm.org/D8292

rebase: mention -r argument in synopsis I'm guessing that we simply forgot to mention it there. I was wondering if maybe `-r` was experimental as long as evolution is, but that doesn't seem to be the case (`-r` is not marked experimental). Differential Revision: https://phab.mercurial-scm.org/D8295

rebase: remove unused defaults argument values from _definedestmap() The caller always provides values for these arguments. Differential Revision: https://phab.mercurial-scm.org/D8291