tests: accept alternative privileged port allocation failure This registers an additional failure message on failed privileged port allocation, equally funcionally valid but previously not handled and causing the test to fail when run in the NixOS sandbox. Differential Revision: https://phab.mercurial-scm.org/D11741

tests: allow the true command to be provided by coreutils The `true` command is sometimes provided as a symbolic link to the `coreutils` single binary. This is the case on NixOS, on which the test was failing because the symbolic link fully resolves to the latter name, equally valid but not previously accepted by the test's golden output. Differential Revision: https://phab.mercurial-scm.org/D11740

tests: add guard check for suid support This adds a check for setuid and setgid support and guards a part of a test requiring this particular filesystem feature. Such feature is notably missing in the Nix/NixOS build sandbox and was causing the whole test to fail for the mercurial package. Differential Revision: https://phab.mercurial-scm.org/D11739

rhg: more efficient `HgPath::join` This commit makes `HgPath::join` slightly more efficient by avoiding one copy. It also avoids a particularly inefficient (quadratic) use of `HgPath::join` by using a new mutating function `HgPathBuf::push` instead. The name for `HgPathBuf::push` is chosen by analogy to `PathBuf::push`. Differential Revision: https://phab.mercurial-scm.org/D11721

relnotes: update 6.0 with the last changes for the release Differential Revision: https://phab.mercurial-scm.org/D11742

rhg: Fix `rhg status` file content comparison This is only used when a file’s metadata make its status ambiguous, which depends on timing of previous command executions. Differential Revision: https://phab.mercurial-scm.org/D11743