Re: [gentoo-dev] [pre-GLEP] Repository configuration file (layout.conf)

[John Helmert III]

On Wed, May 19, 2021 at 02:32:27PM +0200, Michał Górny wrote:
> Hi,
>
> Please review the pre-GLEP inlined below.  Its purpose is to formally
> define the format of layout.conf.  It's pretty much inevitable these
> days, so we should specify it.  However, it doesn't really fit into PMS,
> and other formats (Manifests, metadata.xml) are already defined
> in GLEPs, so this just follows suit.
>
> Pre-GLEP follows.
>
> ---
> GLEP: 9999
> Title: Repository configuration file (layout.conf)
> Author: Michał Górny <mgorny@g.o>
> Type: Standards Track
> Status: Draft
> Version: 1.0
> Created: 2021-05-19
> Last-Modified: 2021-05-19
> Post-History: 2021-05-19
> Content-Type: text/x-rst
> ---
>
> Abstract
> ========
>
> The ``metadata/layout.conf`` file format is specified as used by Portage
> and PkgCore.  A standard set of configuration keys is described

I can't speak for pkgcore but I can't find anywhere this capitalization
scheme is used. Internally and in its docs it seems 'Pkgcore' is used at
the beginning of sentences, but generally 'pkgcore' is used.

> including the keys currently used in the Gentoo repository.
>
>
> Motivation
> ==========
>
> The ``metadata/layout.conf`` file was first added to the Gentoo
> repository in Oct 2011, to facilitate setting of hashes used
> in Manifest2 files.  In Mar 2012, it was used to indicate the transition
> to the new ``md5-dict`` cache format.  In Jul 2013, it started being
> used to indicate the repository's masters and effectively became
> obligatory for all repositories.
>
> Today, ``layout.conf`` is used for various repository configuration
> knobs that can be expressed as simple values and therefore
> do not justify adding new files to the repository.  This primarily
> involves the configuration of development tools but also includes a few
> keys relevant to the behavior of the package manager.
>
> However, ``layout.conf`` is currently not covered by any formal
> specification.  The PMS neglects its existence entirely, and the keys
> used are roughly defined by their first use of Portage or PkgCore.
> This GLEP aims to overcome this by providing a formal specification
> for the file, as well as an up-to-date list of permitted configuration
> keys.
>
>
> Specification
> =============
>
> layout.conf file format
> -----------------------
>
> Every ebuild repository must contain a ``metadata/layout.conf`` file.
> The file uses a line-oriented text format.  Lines starting with ``#``
> represent comments and are ignored, as are lines consisting entirely
> of whitespace.  The remaining lines must contain a key followed
> by equals sign (``=``), followed by a (possibly empty) value.  Each of

"...followed by zero or more space separated values" would be better I
think. Currently it reads like only one value is allowed.

> these elements can be surrounded by additional whitespace that
> is stripped.
>
>
> Configuration keys
> ------------------
>
> The ``layout.conf`` file must contain the ``masters`` key.  Other keys
> listed in this specification are entirely optional.  The package
> managers may choose to implement a subset of listed keys.  Unknown keys
> must be ignored.
>
> The following keys are currently defined:
>
> masters = <space-separated values>
>   Specifies the master repositories of this repository.  For stand-alone
>   repositories, this must be set to an empty value.  Otherwise, it can
>   list one or more repositories, separated by spaces.  This key must
>   be specified.
>
> manifest-hashes = <space-separated values>
>   Specifies the list of hashes that should be used for new distfiles
>   in the Manifest files.  The development tools may create a subset
>   of the specified hashes if it is not updating the checksums for
>   the specified distfile, or does not support the hash in question.
>   The hash names are specified in GLEP 74.  [#GLEP74]_  The default
>   set of hashes is implementation-defined.
>
> manifest-required-hashes = <space-separated values>
>   Specifies the list of hashes that must be used in Manifest files.
>   The development tools must support all the hashes listed there,
>   and update distfile checksums to use these hashes (refetching
>   if necessary).  This must be a subset of manifest-hashes.  If not
>   specified, all hashes from manifest-hashes (or the default set)
>   are considered required.
>
> use-manifests = ``strict``, ``true`` or ``false``
>   Indicates the policy for creating and using Manifest files.  If set
>   to ``strict``, Manifest files are created and files are required to
>   match digests found in Manifests.  If set to ``true``, Manifests
>   are created but digest mismatches are ignored.  If set to ``false``,
>   Manifests are not used at all.  The default is ``strict``.
>
> update-changelog = ``true`` or ``false``
>   Indicates whether the development tools should write ChangeLog files.
>   The default is ``false``.
>
> cache-formats = <space-separated values>
>   Specifies one or more cache formats used by the repository.
>   The currently defined values are ``pms`` for the original format
>   specified in the PMS and ``md5-dict`` for the md5-dict format
>   introduced in Portage 2.2.0_alpha68.  The default is
>   implementation-defined.
>
> eapis-deprecated = <space-separated values>
>   Specifies one or more EAPIs that are to be considered deprecated
>   by the development tools for use in ebuilds, i.e. their use should
>   trigger a warning.  If not specified, no EAPIs are deprecated.
>
> eapis-banned = <space-separated values>
>   Specifies one or more EAPIs that are to be considered banned
>   by the development tools for use in ebuilds, i.e. their use should
>   be blocked.  If not specified, no EAPIs are banned.
>
> repo-name = <string>
>   Specifies the repository name.  If specified, it must be equal
>   to the contents of ``profiles/repo_name``.  If not specified,
>   it defaults to the same value.  Discouraged.
>
> aliases = <space-separated values>
>   Specified one or more additional names that can be used to reference
>   the repository (e.g. in repository dependencies).  If not specified,
>   no aliases are defined.
>
> thin-manifests = ``true`` or ``false``
>   If enabled, Manifest files in the package directory must contain only
>   ``DIST`` entries.  If disabled, Manifest files in the package
>   directory must list digests for all files found in the package
>   directory and the files directory.  The default is ``false``.
>
> sign-commits = ``true`` or ``false``
>   Indicates whether git commits are to be signed (using ``git commit
>   --gpg-sign``.  The default is ``false``.
>
> sign-manifests = ``true`` or ``false``
>   Indicates whether individual package Manifests should be PGP-signed.
>   Note that this refers to the historical behavior of signing individual
>   Manifests, not the GLEP 74 behavior of signing the top-level Manifest.
>   [#GLEP74]_  The default is ``true`` if PGP signing is configured.
>
> properties-allowed = <space-separated values>
>   Specifies the list of ``PROPERTIES`` tokens that are permitted
>   to be used in ebuilds.  If present, the development tools should issue
>   a warning if ``PROPERTIES`` contains any tokens that are not listed
>   here.  If not specified, all tokens are permitted.
>
> restrict-allowed = <space-separated values>
>   Same as properties-allowed, except for ``RESTRICT``.
>
> profile-formats = <space-separated values>
>   Specifies the format used by profiles and/or extensions to it.
>   The default is ``pms`` indicating the format specified in the PMS.
>   Other values are implementation-defined.
>
>
> It is recommended that any future keys are added to this GLEP before
> being implemented.
>
>
> Example
> -------
>
> The following is an example configuration for a git repository with
> Gentoo set as a master::
>
>     masters = gentoo
>
>     # git: do not use ChangeLog, use thin, unsigned Manifests
>     update-changelog = false
>     thin-manifests = true
>     sign-manifests = false
>
>     # force the new md5-dict cache format
>     cache-formats = md5-dict
>
>
> Rationale
> =========
>
> This GLEP is written almost 10 years after ``layout.conf`` was
> originally introduced.  This made it necessary to write it in such a way
> that both the modern and historical implementations in Portage
> and PkgCore, as well as the use in the Gentoo repository
> and a reasonably large subset of the other repositories would remain
> compliant.
>
> The historical default of assuming ``masters = gentoo`` when unspecified
> is omitted as it is not portable and verbosely deprecated for many
> years in Portage.  All repositories are required to explicitly specify
> their masters, or an empty value if they are stand-alone.
>
> The default for Manifest hashes and cache formats are left to be
> implementation-defined, as the defaults changed over time and do not
> match between package managers.  In particular, Portage attempts to
> autodetect the cache format currently used in a given repository.
>
> The repo-name key has been originally added as an alternative to
> ``profiles/repo_name``.  However, the latter file is still required
> for PMS compliance.  Furthermore, given that it is much easier to parse,
> there seems to be no appealing reason to work towards replacing that
> file.  This means that for all practical reasons, the repo-name key
> is redundant and is listed here for completeness only.
>
> The profile-formats key has been introduced to permit Portage-specific
> extensions to the profile directory without having to introduce custom
> EAPIs.  The exact extensions are considered outside the scope of this
> specification.
>
>
> Backwards Compatibility
> =======================
>
> The existing implementations found in Portage and PkgCore conform
> to this specification, so does the ``metadata/layout.conf`` file
> found in the Gentoo repository.
>
>
> Reference Implementation
> ========================
>
> The support for ``metadata/layout.conf`` is already a part of Portage
> and PkgCore.
>
>
> References
> ==========
>
> .. [#GLEP74] GLEP 74: Full-tree verification using Manifest files
>    (https://www.gentoo.org/glep/glep-0074.html)
>
>
> Copyright
> =========
>
> This work is licensed under the Creative Commons Attribution-ShareAlike
> 4.0
> International License. To view a copy of this license, visit
> https://creativecommons.org/licenses/by-sa/4.0/.
>
>
> --
> Best regards,
> Michał Górny
>
>
>