This page explains the storage format of Gerrit’s project configuration and access control models.

The web UI access control panel is a front end for human-readable configuration files under the refs/meta/config namespace in the affected project. Direct manipulation of these files is mainly relevant in an automation scenario of the access controls.

The refs/meta/config namespace

The namespace contains three different files that play different roles in the permission model. With read permission to that reference, it is possible to fetch the refs/meta/config reference to a local repository. A nice side effect is that you can also upload changes to project permissions and review them just like with regular code changes. The preview changes option is also provided on the UI. Please note that you will have to configure push rights for the refs/meta/config name space if you’d like to use the possibility to automate permission updates.

The file project.config

The project.config file contains the link between groups and their permitted actions on reference patterns in this project and any projects that inherit its permissions.

The format in this file corresponds to the Git config file format, so if you want to automate your permissions it is a good idea to use the git config command when writing to the file. This way you know you don’t accidentally break the format of the file.

Here follows a git config command example:

$ git config -f project.config project.description "Rights inherited by all other projects"

Below you will find an example of the project.config file format:

[project]
       description = Rights inherited by all other projects
[access "refs/*"]
       read = group Administrators
[capability]
       administrateServer = group Administrators
[receive]
       requireContributorAgreement = false

As you can see, there are several sections.

The project section appears once per project.

The access section appears once per reference pattern, such as refs/* or refs/heads/*. Only one access section per pattern is allowed. You will find examples of keys and values in each category section below.

The receive section appears once per project.

The submit section appears once per project.

The capability section only appears once, and only in the All-Projects repository. It controls core features that are configured on a global level. You can find examples of these below.

Project section

The project section includes configuration of project settings.

These are the keys:

  • Description

Receive section

The receive section includes configuration of project-specific receive settings:

receive.requireContributorAgreement

Controls whether or not a user must complete a contributor agreement before they can upload changes. Default is INHERIT. If All-Project enables this option then the dependent project must set it to false if users are not required to sign a contributor agreement prior to submitting changes for that specific project. To use that feature the global option in gerrit.config must be enabled: auth.contributorAgreements.

receive.requireSignedOffBy

Sign-off can be a requirement for some projects (for example Linux kernel uses it). Sign-off is a line at the end of the commit message which certifies who is the author of the commit. Its main purpose is to improve tracking of who did what, especially with patches. Default is INHERIT, which means that this property is inherited from the parent project.

receive.requireChangeId

Controls whether or not the Change-Id must be included in the commit message in the last paragraph. Default is INHERIT, which means that this property is inherited from the parent project.

receive.maxObjectSizeLimit

Maximum allowed Git object size that receive-pack will accept. If an object is larger than the given size the pack-parsing will abort and the push operation will fail. If set to zero then there is no limit.

Project owners can use this setting to prevent developers from pushing objects which are too large to Gerrit. This setting can also be set it gerrit.config globally receive.maxObjectSizeLimit.

The project specific setting in project.config is only honored when it further reduces the global limit.

Default is zero.

Common unit suffixes of k, m, or g are supported.

receive.checkReceivedObjects

Controls whether or not the JGit functionality for checking received objects is enabled.

By default Gerrit checks the validity of git objects. Setting this variable to false should not be used unless a project with history containing invalid objects needs to be pushed into a Gerrit repository.

This functionality is provided as some other git implementations have allowed bad history to be written into git repositories. If these repositories need pushing up to Gerrit then the JGit checks need to be disabled.

The default value for this is true, false disables the checks.

Submit section

The submit section includes configuration of project-specific submit settings:

  • mergeContent: Defines whether to automatically merge changes. Valid values are true, false, or INHERIT. Default is INHERIT.

  • action: defines the submit type. Valid values are fast forward only, merge if necessary, rebase if necessary, merge always and cherry pick. The default is merge if necessary.

Merge strategy

Access section

Each access section includes a reference and access rights connected to groups. Each group listed must exist in the groups file.

Please refer to the Access Categories documentation for a full list of available access rights.

MIME Types section

The mimetype section may be configured to force the web code reviewer to return certain MIME types by file path. MIME types may be used to activate syntax highlighting.

[mimetype "text/x-c"]
  path = *.pkt
[mimetype "text/x-java"]
  path = api/current.txt

Capability section

The capability section only appears once, and only in the All-Projects repository. It controls Gerrit administration capabilities that are configured on a global level.

Please refer to the Global Capabilities documentation for a full list of available capabilities.

branchOrder section

Defines a branch ordering which is used for backporting of changes. Backporting will be offered for a change (in the Gerrit UI) for all more stable branches where the change can merge cleanly.

branchOrder.branch

A branch name, typically multiple values will be defined. The order of branch names in this section defines the branch order. The topmost is considered to be the least stable branch (typically the master branch) and the last one the most stable (typically the last maintained release branch).

Example:

[branchOrder]
  branch = master
  branch = stable-2.9
  branch = stable-2.8
  branch = stable-2.7

The branchOrder section is inheritable. This is useful when multiple or all projects follow the same branch rules. A branchOrder section in a child project completely overrides any branchOrder section from a parent i.e. there is no merging of branchOrder sections. A present but empty branchOrder section removes all inherited branch order.

Branches not listed in this section will not be included in the mergeability check. If the branchOrder section is not defined then the mergeability of a change into other branches will not be done.

The file groups

Each group in this list is linked with its UUID so that renaming of groups is possible without having to rewrite every groups file in every repository where it’s used.

This is what the default groups file for All-Projects.git looks like:

# UUID                                         Group Name
#
3d6da7dc4e99e6f6e5b5196e21b6f504fc530bba       Administrators
global:Anonymous-Users                         Anonymous Users
global:Project-Owners                          Project Owners
global:Registered-Users                        Registered Users

This file can’t be written to by the git config command.

In order to reference a group in project.config, it must be listed in the groups file. When editing permissions through the web UI this file is maintained automatically, but when pushing updates to refs/meta/config this must be dealt with by hand. Gerrit will refuse project.config files that refer to groups not listed in groups.

The UUID of a group can be found on the General tab of the group’s page in the web UI or via the -v option to the ls-groups SSH command.

The file rules.pl

The rules.pl files allows you to replace or amend the default Prolog rules that control e.g. what conditions need to be fulfilled for a change to be submittable. This file content should be interpretable by the Prolog Cafe interpreter.

You can read more about the rules.pl file and the prolog rules on the Prolog cookbook page.

Part of Gerrit Code Review