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.

Property inheritance

If a property is set to INHERIT, then the value from the parent project is used. If the property is not set in any parent project, the default value is FALSE.

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
[access "refs/heads/*"]
        label-Your-Label-Here = -1..+1 group Administrators
[capability]
       administrateServer = group Administrators
[receive]
       requireContributorAgreement = false
[label "Your-Label-Here"]
        function = MaxWithBlock
        value = -1 Your -1 Description
        value =  0 Your No score Description
        value = +1 Your +1 Description

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.

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.

The label section can appear multiple times. You can also redefine the text and behavior of the built in label types Code-Review and Verified.

Optionally a commentlink section can be added to define project-specific comment links. The commentlink section has the same format as the commentlink section in gerrit.config which is used to define global comment links.

Project section

The project section includes configuration of project settings.

These are the keys:

description

A description for the project.

state

This setting defines the state of the project. A project can have the following states:

  • Active:

    The project is active and users can see and modify the project according to their access rights on the project.

  • Read Only:

    The project is read only and all modifying operations on it are disabled. E.g. this means that pushing to this project fails for all users even if they have push permissions assigned on it.

    Setting a project to this state is an easy way to temporary close a project, as you can keep all write access rights in place and they will become active again as soon as the project state is set back to Active.

    This state also makes sense if a project was moved to another location. In this case all new development should happen in the new project and you want to prevent that somebody accidentally works on the old project, while keeping the old project around for old references.

  • Hidden:

    The project is hidden and only visible to project owners. Other users are not able to see the project even if they have read permissions granted on the project.

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

The Require Change-Id in commit message option defines whether a Change-Id in the commit message is required for pushing a commit for review. If this option is set, trying to push a commit for review that doesn’t contain a Change-Id in the commit message fails with missing Change-Id in commit message footer.

It is recommended to set this option and use a commit-msg hook (or other client side tooling like EGit) to automatically generate Change-Id’s for new commits. This way the Change-Id is automatically in place when changes are reworked or rebased and uploading new patch sets gets easy.

If this option is not set, commits can be uploaded without a Change-Id, but then users have to remember to copy the assigned Change-Id from the change screen and insert it manually into the commit message when they want to upload a second patch set.

Default is INHERIT, which means that this property is inherited from the parent project. The global default for new hosts is true

This option is deprecated and future releases will behave as if this is always true.

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 in gerrit.config globally ( receive.maxObjectSizeLimit).

The project specific setting in project.config may not set a value higher than the global limit (if configured). In other words, it is only honored when it further reduces the global limit.

When receive.inheritProjectmaxObjectSizeLimit is enabled in the global config, the value is inherited from the parent project. Otherwise, it is not inherited and must be explicitly set per project.

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.

receive.enableSignedPush

Controls whether server-side signed push validation is enabled on the project. Only has an effect if signed push validation is enabled on the server; see the global configuration for details.

Default is INHERIT, which means that this property is inherited from the parent project.

receive.requireSignedPush

Controls whether server-side signed push validation is required on the project. Only has an effect if signed push validation is enabled on the server, and receive.enableSignedPush is set on the project. See the global configuration for details.

Default is INHERIT, which means that this property is inherited from the parent project.

receive.rejectImplicitMerges

Controls whether a check for implicit merges will be performed when changes are pushed for review. An implicit merge is a case where merging an open change would implicitly merge another branch into the target branch. Typically, this happens when a change is done on master and, by mistake, pushed to a stable branch for review. When submitting such change, master would be implicitly merged into stable without anyone noticing that. When this option is set to 'true' Gerrit will reject the push if an implicit merge is detected.

This check is only done for non-merge commits, merge commits are not subject of the implicit merge check.

Default is INHERIT, which means that this property is inherited from the parent project.

receive.createNewChangeForAllNotInTarget

The create-new-change-for-all-not-in-target option provides a convenience for selecting the merge base by setting it automatically to the target branch’s tip so you can create new changes for all commits not in the target branch.

This option is disabled if the tip of the push is a merge commit.

This option also only works if there are no merge commits in the commit chain, in such cases it fails warning the user that such pushes can only be performed by manually specifying bases

This option is useful if you want to push a change to your personal branch first and for review to another branch for example. Or in cases where a commit is already merged into a branch and you want to create a new open change for that commit on another branch.

Change section

The change section includes configuration for project-specific change settings:

change.privateByDefault

Controls whether all new changes in the project are set as private by default.

Note that a new change will be public if the is_private field in ChangeInput is set to false explicitly when calling the CreateChange REST API or the remove-private PushOption is used during the Git push.

Default is INHERIT, which means that this property is inherited from the parent project.

change.workInProgressByDefault

Controls whether all new changes in the project are set as WIP by default.

Note that a new change will be ready if the workInProgress field in ChangeInput is set to false explicitly when calling the CreateChange REST API or the ready PushOption is used during the Git push.

Default is INHERIT, which means that this property is inherited from the parent project.

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'.

  • 'matchAuthorToCommitterDate': Defines whether to the author date will be changed to match the submitter date upon submit, so that git log shows when the change was submitted instead of when the author last committed. Valid values are 'true', 'false', or 'INHERIT'. The default is 'INHERIT'. This option only takes effect in submit strategies which already modify the commit, i.e. Cherry Pick, Rebase Always, and (perhaps) Rebase If Necessary.

  • 'rejectEmptyCommit': Defines whether empty commits should be rejected when a change is merged. Changes might not seem empty at first but when attempting to merge, rebasing can lead to an empty commit. If this option is set to 'true' the merge would fail. An empty commit is still allowed as the initial commit on a branch.

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.

Label section

Please refer to Custom Labels documentation.

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.

reviewer section

Defines config options to adjust a project’s reviewer workflow such as enabling reviewers and CCs by email.

reviewer.enableByEmail

A boolean indicating if reviewers and CCs that do not currently have a Gerrit account can be added to a change by providing their email address.

This setting only takes affect for changes that are readable by anonymous users.

Default is INHERIT, which means that this property is inherited from the parent project. If the property is not set in any parent project, the default value is FALSE.

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:Change-Owner                            Change Owner
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.

Submit Type

The method Gerrit uses to submit a change to a project can be modified by any project owner through the project console, Projects > List > my/project. In general, a submitted change is only merged if all its dependencies are also submitted, with exceptions documented below. The following submit types are supported:

  • Inherit

    This is the default for new projects, unless overridden by a global defaultSubmitType option.

    Inherit the submit type from the parent project. In All-Projects, this is equivalent to Merge If Necessary.

  • Fast Forward Only

    With this method no merge commits are produced. All merges must be handled on the client, prior to uploading to Gerrit for review.

    To submit a change, the change must be a strict superset of the destination branch. That is, the change must already contain the tip of the destination branch at submit time.

  • Merge If Necessary

    If the change being submitted is a strict superset of the destination branch, then the branch is fast-forwarded to the change. If not, then a merge commit is automatically created. This is identical to the classical git merge behavior, or git merge --ff.

  • Always Merge

    Always produce a merge commit, even if the change is a strict superset of the destination branch. This is identical to the behavior of git merge --no-ff, and may be useful if the project needs to follow submits with git log --first-parent.

  • Cherry Pick

    Always cherry pick the patch set, ignoring the parent lineage and instead creating a brand new commit on top of the current branch head.

    When cherry picking a change, Gerrit automatically appends onto the end of the commit message a short summary of the change’s approvals, and a URL link back to the change on the web. The committer header is also set to the submitter, while the author header retains the original patch set author.

    Note that Gerrit ignores dependencies between changes when using this submit type unless change.submitWholeTopic is enabled and depending changes share the same topic. So generally submitters must remember to submit changes in the right order when using this submit type. If all you want is extra information in the commit message, consider using the Rebase Always submit strategy.

  • Rebase If Necessary

    If the change being submitted is a strict superset of the destination branch, then the branch is fast-forwarded to the change. If not, then the change is automatically rebased and then the branch is fast-forwarded to the change.

When Gerrit tries to do a merge, by default the merge will only succeed if there is no path conflict. A path conflict occurs when the same file has also been changed on the other side of the merge.

  • Rebase Always

    Basically, the same as Rebase If Necessary, but it creates a new patchset even if fast forward is possible AND like Cherry Pick it ensures footers such as Change-Id, Reviewed-On, and others are present in resulting commit that is merged.

Thus, Rebase Always can be considered similar to Cherry Pick, but with the important distinction that Rebase Always does not ignore dependencies.

Allow content merges

If Allow content merges is enabled, Gerrit will try to do a content merge when a path conflict occurs.

Part of Gerrit Code Review