![Stefan Beller](/assets/img/avatar_default.png)
This eases the way of handling many different branches for the superproject subscription. As the superproject subscriptions are not yet in a release, we can still play around with them. When a user sees "refs = refs/heads/*:refs/heads/*" they cannot tell whether this is 1:1 matching or any match to any match without consulting the documentation. Differentiate the matching strategy by keys, such that we have "all = <refspec>" as well as "matching = <refspec>". The "all" key implies there is no interaction between the wildcards on the left and right side, e.g. all=refs/heads/*:refs/heads* indicates that any branch can be subscribed to any other branch in the given superproject. "matching" however substitutes the wildcard on the right with the captured value on the left. matching=refs/heads/*:refs/heads* allows a subscription of refs/heads/foo in the submodule to the refs/heads/foo in the superproject. Change-Id: I84d3a72c00f76570798880adf54ce56f974466ff
255 lines
10 KiB
Plaintext
255 lines
10 KiB
Plaintext
= Gerrit Code Review - Superproject subscription to submodules updates
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[[automatic_update]]
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== Description
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Gerrit supports a custom git superproject feature for tracking submodules.
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This feature is useful for automatic updates on superprojects whenever
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a change is merged on tracked submodules.
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When a superproject is subscribed to a submodule, it is not
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required to push/merge commits to this superproject to update the
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gitlink to the submodule. Whenever a commit is merged in a submodule,
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its subscribed superproject is updated by Gerrit.
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Imagine a superproject called 'super' having a branch called 'dev'
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having subscribed to a submodule 'sub' on a branch 'dev-of-sub'. When a commit
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is merged in branch 'dev-of-sub' of 'sub' project, Gerrit automatically
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creates a new commit on branch 'dev' of 'super' updating the gitlink
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to point to the just merged commit.
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To take advantage of this feature, one should:
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. ensure superproject subscriptions are enabled on the server via
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link:config-gerrit.html#submodule.enableSuperProjectSubscriptions[submodule.enableSuperProjectSubscriptions]
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. configure the submodule to allow having a superproject subscribed
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. ensure the .gitmodules file of the superproject includes
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.. a branch field
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.. a url that starts with the link:config-gerrit.html#gerrit.canonicalWebUrl[`gerrit.canonicalWebUrl`]
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When a commit in a project is merged, Gerrit checks for superprojects
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that are subscribed to the the project and automatically updates those
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superprojects with a commit that updates the gilink for the project.
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This feature is enabled by default and can be disabled
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via link:config-gerrit.html#submodule.enableSuperProjectSubscriptions[submodule.enableSuperProjectSubscriptions]
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in the server configuration.
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== Git submodules overview
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Submodules are a Git feature that allows an external repository to be
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attached inside a repository at a specific path. The objective here
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is to provide a brief overview, further details can be found
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in the official Git submodule documentation.
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Imagine a repository called 'super' and another one called 'sub'.
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Also consider 'sub' available in a running Gerrit instance on "server".
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With this feature, one could attach 'sub' inside of 'super' repository
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at path 'sub' by executing the following command when being inside
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'super':
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----
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git submodule add ssh://server/sub sub
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----
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Still considering the above example, after its execution notice that
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inside the local repository 'super' the 'sub' folder is considered a
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gitlink to the external repository 'sub'. Also notice a file called
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.gitmodules is created (it is a configuration file containing the
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subscription of 'sub'). To provide the SHA-1 each gitlink points to in
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the external repository, one should use the command:
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----
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git submodule status
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----
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In the example provided, if 'sub' is updated and 'super' is supposed
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to see the latest SHA-1 (considering here 'sub' has only the master
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branch), one should then commit the modified gitlink for 'sub' in
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the 'super' project. Actually it would not even need to be an
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external update, one could move to 'sub' folder (inside 'super'),
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modify its content, commit, then move back to 'super' and
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commit the modified gitlink for 'sub'.
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== Creating a new subscription
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=== Ensure the subscription is allowed
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Gerrit has a complex access control system, where different repositories
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can be accessed by different groups of people. To ensure that the submodule
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related information is allowed to be exposed in the superproject,
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the submodule needs to be configured to enable the superproject subscription.
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In a submodule client, checkout the refs/meta/config branch and edit
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the subscribe capabilities in the 'project.config' file:
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----
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git fetch <remote> refs/meta/config:refs/meta/config
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git checkout refs/meta/config
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$EDITOR project.config
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----
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and add the following lines:
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----
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[allowSuperproject "<superproject>"]
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matching = <refspec>
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----
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where the 'superproject' should be the exact project name of the superproject.
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The refspec defines which branches of the submodule are allowed to be
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subscribed to which branches of the superproject. See below for
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link:#acl_refspec[details]. Push the configuration for review and
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submit the change:
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----
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git add project.config
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git commit -m "Allow <superproject> to subscribe"
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git push <remote> HEAD:refs/for/refs/meta/config
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----
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After the change is integrated a superproject subscription is possible.
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The configuration is inherited from parent projects, such that you can have
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a configuration in the "All-Projects" project like:
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----
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[allowSuperproject "my-only-superproject"]
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matching = refs/heads/*:refs/heads/*
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----
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and then you don't have to worry about configuring the individual projects
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any more. Child projects cannot negate the parent's configuration.
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=== Defining the submodule branch
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Since Gerrit manages subscriptions in the branch scope, we could have
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a scenario having a project called 'super' having a branch 'integration'
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subscribed to a project called 'sub' in branch 'integration', and also
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having the same 'super' project but in branch 'dev' subscribed to the 'sub'
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project in a branch called 'local-dev'.
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After adding the git submodule to a super project, one should edit
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the .gitmodules file to add a branch field to each submodule
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section which is supposed to be subscribed.
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As the branch field is a Gerrit-specific field it will not be filled
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automatically by the git submodule command, so one needs to edit it
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manually. Its value should indicate the branch of a submodule project
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that when updated will trigger automatic update of its registered
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gitlink.
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The branch value could be "'.'" if the submodule project branch
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has the same name as the destination branch of the commit having
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gitlinks/.gitmodules file.
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If the intention is to make use of the Gerrit feature described
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here, one should always be sure to update the .gitmodules file after
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adding submodules to a super project.
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If a git submodule is added but the branch field is not added to the
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.gitmodules file, Gerrit will not create a subscription for the
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submodule and there will be no automatic updates to the superproject.
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Whenever a commit is merged to a project, its project config is checked
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to see if any potential superprojects are allowed to subscribe to it.
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If so, the superproject is checked if a valid subscription exists
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by checking the .gitmodules file for the a submodule which includes
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a `branch` field and a url pointing to this server.
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[[acl_refspec]]
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=== The RefSpec in the allowSuperproject section
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There are two options for specifying which branches can be subscribed
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to. The most common is to set `allowSuperproject.<superproject>.matching`
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to a Git-style refspec, which has the same syntax as the refspecs used
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for pushing in Git. Regular expressions as found in the ACL configuration
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are not supported.
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The most restrictive refspec is allowing one specific branch of the
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submodule to be subscribed to one specific branch of the superproject:
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----
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[allowSuperproject "<superproject>"]
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matching = refs/heads/<submodule-branch>:refs/heads/<superproject-branch>
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----
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If you want to allow for a 1:1 mapping, i.e. 'master' maps to 'master',
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'stable' maps to 'stable', but not allowing 'master' to be subscribed to
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'stable':
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----
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[allowSuperproject "<superproject>"]
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matching = refs/heads/*:refs/heads/*
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----
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To allow all refs matching one pattern to subscribe to all refs
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matching another pattern, set `allowSuperproject.<superproject>.all`
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to the patterns concatenated with a colon. For example, to make a
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single branch available for subscription from all branches of the
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superproject:
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----
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[allowSuperproject "<superproject>"]
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all = refs/heads/<submodule-branch>:refs/heads/*
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----
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To make all branches available for subscription from all branches of
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the superproject:
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----
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[allowSuperproject "<superproject>"]
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all = refs/heads/*:refs/heads/*
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----
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=== Subscription Limitations
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Gerrit will only automatically update superprojects where the
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submodules are hosted on the same Gerrit instance as the
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superproject. Gerrit determines this by checking the hostname of the
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submodule specified in the .gitmodules file and comparing it to the
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hostname from the link:config-gerrit.html#gerrit.canonicalWebUrl[`gerrit.canonicalWebUrl`].
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It is currently not possible to use the submodule subscription feature
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with a canonical web URL hostname that differs from the hostname of
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the submodule. Instead relative submodules should be used.
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The Gerrit instance administrator group should always certify to
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provide the canonical web URL value in its configuration file. Users
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should certify to use the correct hostname of the running Gerrit
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instance to add/subscribe submodules.
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=== Relative submodules
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To enable easier usage of Gerrit mirrors and/or distribution over
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several protocols, such as plain git and HTTP(S) as well as SSH, one
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can use relative submodules. This means that instead of providing the
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entire URL to the submodule a relative path is stated in the
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.gitmodules file.
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Gerrit will try to match the entire project name of the submodule
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including directories. Therefore it is important to supply the full
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path name of the Gerrit project, not only relative to the super
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repository. See the following example:
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We have a super repository placed under a sub directory.
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product/super_repository.git
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To this repository we wish add a submodule "deeper" into the directory
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structure.
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product/framework/subcomponent.git
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Now we need to edit the .gitmodules to include the complete path to
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the Gerrit project. Observe that we need to use two "../" to include
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the complete Gerrit project path.
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path = subcomponent.git
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url = ../../product/framework/subcomponent.git
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branch = master
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In contrast the following will not setup proper submodule
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subscription, even if the submodule will be successfully cloned by git
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from Gerrit.
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path = subcomponent.git
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url = ../framework/subcomponent.git
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branch = master
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== Removing Subscriptions
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To remove a subscription, either disable the subscription from the
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submodules configuration or remove the submodule or information thereof
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(such as the branch field) in the superproject.
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GERRIT
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------
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Part of link:index.html[Gerrit Code Review]
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SEARCHBOX
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---------
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