Pov-fabric-helpers

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- Nothing changed yet.

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- ``register_host_key()`` now takes ``fingerprints`` so you can specify both
MD5 and SHA256 fingerprints.

Use either ``register_host_key(key, fingerprint=md5_fprint)`` or
``register_host_key(key, fingerprints=[md5_fprint, sha256_fprint])``.

- Low-level helper ``ssh_key_fingerprint()`` now takes ``force_md5`` so you
can insist on MD5 instead of whatever OpenSSH gives you by default (which is
SHA256 for modern OpenSSH).

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- New helpers:

- ``git_update()``, ``register_host_key()``,
- ``ensure_locales()``,
- ``changelog_banner()``, ``run_and_changelog()``,
``has_new_changelog_message()``,
- ``install_missing_packages()``, ``package_available()``,
- ``upload_file()``, ``generate_file()``, ``ensure_directory()``,
``download_file()``,
- ``install_postfix_virtual_table()``,
- ``install_apache_website()``,
- ``ensure_ssl_key()``.

- New optional arguments for existing helpers:

- ``git_clone()`` now takes ``branch`` and ``changelog``.
- ``ensure_user()`` now takes ``shell``, ``home``, ``create_home``, and
``changelog``.
- ``install_packages()`` now takes ``changelog``.
- ``changelog()`` now takes ``context``.
- ``changelog_append()`` now takes ``context`` and ``optional``.
- ``changelog_banner()`` now takes ``context`` and ``optional``.

- Increased safety:

- all helpers check their arguments for unsafe shell metacharacters.
- changelog() and friends quote the arguments correctly.

- Improved instance API:

- allow ``str.format(**instance)`` (by making Instance a subclass of
``dict``).
- allow instance aliases defined via ``Instance.define_alias(alias, name)``
static method.

- Bugfixes:

- ``ensure_postgresql_db()`` now works correctly on Ubuntu 14.04.
- ``run_as_root`` now correctly handles ``env.host_string`` with no
username part.

- New low-level helpers you're probably not interested in, unless you're
writing your own helpers:

- ``aslist()``, ``assert_shell_safe()``,
- ``ssh_key_fingerprint()``,
- ``render_jinja2()``, ``render_sinterp()``,
- ``parse_git_repo()``,
- ``generate_ssl_config()``, ``generate_ssl_key()``, ``generate_ssl_csr()``,
- ``get_postfix_setting()``, ``parse_postfix_setting()``,
``add_postfix_virtual_map()``, ``add_postfix_setting()``,
- ``run_as_root()``.

----------------

- First public release.

- Helpers:

- ``ensure_apt_not_outdated()``, ``package_installed()``,
``install_packages()``,
- ``ensure_known_host()``, ``ensure_user()``,
- ``git_clone()``,
- ``ensure_postgresql_user()``, ``ensure_postgresql_db()``,
- ``changelog()``, ``changelog_append()``.

- Instance API:

- ``class Instance``, ``Instance.with_params()``,
``Instance.REQUIRED``, ``Instance.define()``.
- ``instance._asdict()``.
- ``get_instance()``.

- Low-level helpers you're probably not interested in, unless you're
writing your own helpers:

- ``asbool()``,
- ``postgresql_user_exists()``, ``postgresql_db_exists()``.