test-https: test basic functions of client certificate authentication Because hgweb doesn't support client certificates, I just patched it to require client certificates that are signed and verified by the server certificate. This won't be ideal for production servers, but should be okay for the test. The encrypted key file will be used by future patches. I couldn't figure out a way to redirect a password prompt provided by OpenSSL, so it isn't tested for now.

phases: add `hg help phases` hint to failures to edit public commits There were a couple of locations that were missing this hint after an edition of some kind failed due to the public phase.

phases: rewrite "immutable changeset" to "public changeset" The phrase "cannot edit immutable changeset" is kind of tautological. Of course unchangeable things can't be changed. We instead mention "public" and provide a hint so that we can point to the actual problem. Even in cases where some operation other than edition cannot be performed, "public" gives the root cause that results in the "immutable" effect. There is a precedent for saying "public" instead of "immutable", for example, in `hg commit --amend`.