= Gerrit Code Review - Review Labels

As part of the code review process, reviewers score each change with
values for each label configured for the project.  The label values that
a given user is allowed to set are defined according to the
link:access-control.html#category_review_labels[access controls].  Gerrit
comes pre-configured with the Code-Review label that can be granted to
groups within projects, enabling functionality for that group's members.


[[label_Code-Review]]
== Label: Code-Review

The code review label is the second of two default labels that is
configured upon the creation of a Gerrit instance.  It may have any
meaning the project desires.  It was originally invented by the Android
Open Source Project to mean 'I read the code and it seems reasonably
correct'.

The range of values is:

* -2 This shall not be merged
+
The code is so horribly incorrect/buggy/broken that it must not be
submitted to this project, or to this branch.  This value is valid
across all patch sets in the same change, i.e. the reviewer must
actively change his/her review to something else before the change
is submittable.
+
*Any -2 blocks submit.*

* -1 I would prefer this is not merged as is
+
The code doesn't look right, or could be done differently, but
the reviewer is willing to live with it as-is if another reviewer
accepts it, perhaps because it is better than what is currently in
the project.  Often this is also used by contributors who don't like
the change, but also aren't responsible for the project long-term
and thus don't have final say on change submission.
+
Does not block submit.

* 0 No score
+
Didn't try to perform the code review task, or glanced over it but
don't have an informed opinion yet.

* +1 Looks good to me, but someone else must approve
+
The code looks right to this reviewer, but the reviewer doesn't
have access to the `+2` value for this category.  Often this is
used by contributors to a project who were able to review the change
and like what it is doing, but don't have final approval over what
gets submitted.

* +2 Looks good to me, approved
+
Basically the same as `+1`, but for those who have final say over
how the project will develop.
+
*Any +2 enables submit.*

For a change to be submittable, the latest patch set must have a
`+2 Looks good to me, approved` in this category, and no
`-2 Do not submit`.  Thus `-2` on any patch set can block a submit,
while `+2` on the latest patch set can enable it.

If a Gerrit installation does not wish to use this label in any project,
the `[label "Code-Review"]` section can be deleted from `project.config`
in `All-Projects`.

If a Gerrit installation or project wants to modify the description text
associated with these label values, the text can be updated in the
`label.Code-Review.value` fields in `project.config`.

Additional entries could be added to `label.Code-Review.value` to
further extend the negative and positive range, but there is likely
little value in doing so as this only expands the middle region.  This
label is a `MaxWithBlock` type, which means that the lowest negative
value if present blocks a submit, while the highest positive value is
required to enable submit.

[[label_Verified]]
== Label: Verified

The Verified label was originally invented by the Android Open Source
Project to mean 'compiles, passes basic unit tests'.  Some CI tools
expect to use the Verified label to vote on a change after running.

Administrators can install the Verified label by adding the following
text to `project.config`:

====
  [label "Verified"]
      function = MaxWithBlock
      value = -1 Fails
      value =  0 No score
      value = +1 Verified
====

The range of values is:

* -1 Fails
+
Tried to compile, but got a compile error, or tried to run tests,
but one or more tests did not pass.
+
*Any -1 blocks submit.*

* 0 No score
+
Didn't try to perform the verification tasks.

* +1 Verified
+
Compiled (and ran tests) successfully.
+
*Any +1 enables submit.*

For a change to be submittable, the change must have a `+1 Verified`
in this label, and no `-1 Fails`.  Thus, `-1 Fails` can block a submit,
while `+1 Verified` enables a submit.

Additional values could also be added to this label, to allow it to
behave more like `Code-Review` (below).  Add -2 and +2 entries to the
`label.Verified.value` fields in `project.config` to get the same
behavior.


[[label_custom]]
== Your Label Here

Site administrators and project owners can also define their own labels.

See above for descriptions of how <<label_Verified,`Verified`>>
and <<label_Code-Review,`Code-Review`>> work, and add your own
label to `project.config` to get the same behavior over your own range
of values, for any label you desire.

Just like the built-in labels, users need to be given permissions to
vote on custom labels. Permissions can either be added by manually
editing project.config when adding the labels, or, once the labels are
added, permission categories for those labels will show up in the
permission editor web UI.

Labels may be added to any project's `project.config`; the default
labels are defined in `All-Projects`. Labels are inherited from parent
projects; a child project may add, override, or remove labels defined in
its parents.  Overriding a label in a child project overrides all its
properties and values.  To remove a label in a child project, add an
empty label with the same name as in the parent.

Labels are laid out in the order they are specified in project.config,
with inherited labels appearing first, providing some layout control to
the administrator.

[[label_name]]
=== `label.Label-Name`

The name for a label, consisting only of alphanumeric characters and
`-`.


[[label_value]]
=== `label.Label-Name.value`

A multi-valued key whose values are of the form `"<#> Value description
text"`. The `<#>` may be any positive or negative number with an
optional leading `+`.


[[label_abbreviation]]
=== `label.Label-Name.abbreviation`

An abbreviated name for a label shown as a compact column header, for
example on project dashboards. Defaults to all the uppercase characters
in the label name, e.g. `Label-Name` is abbreviated by default as `LN`.


[[label_function]]
=== `label.Label-Name.function`

The name of a function for evaluating multiple votes for a label.  This
function is only applied if the default submit rule is used for a label.
If you write a link:prolog-cookbook.html#HowToWriteSubmitRules[custom
submit rule] (and do not call the default rule), the function name is
ignored and may be treated as optional.

Valid values are:

* `MaxWithBlock` (default)
+
The lowest possible negative value, if present, blocks a submit, while
the highest possible positive value is required to enable submit. There
must be at least one positive value, or else submit will never be
enabled. To permit blocking submits, ensure a negative value is defined.

* `AnyWithBlock`
+
The lowest possible negative value, if present, blocks a submit, Any
other value enables a submit. To permit blocking submits, ensure
that a negative value is defined.

* `MaxNoBlock`
+
The highest possible positive value is required to enable submit, but
the lowest possible negative value will not block the change.

* `NoBlock`/`NoOp`
+
The label is purely informational and values are not considered when
determining whether a change is submittable.


[[label_copyMinScore]]
=== `label.Label-Name.copyMinScore`

If true, the lowest possible negative value for the label is copied
forward when a new patch set is uploaded.

[[label_copyMaxScore]]
=== `label.Label-Name.copyMaxScore`

If true, the highest possible positive value for the label is copied
forward when a new patch set is uploaded. This can be used to enable
sticky approvals, reducing turn-around for trivial cleanups prior to
submitting a change.

[[label_copyAllScoresOnTrivialRebase]]
=== `label.Label-Name.copyAllScoresOnTrivialRebase`

If true, all scores for the label are copied forward when a new patch
set is uploaded that is a trivial rebase. A new patch set is considered
as trivial rebase if the commit message is the same as in the previous
patch set and if it has the same code delta as the previous patch set.
This is the case if the change was rebased onto a different parent.
This can be used to enable sticky approvals, reducing turn-around for
trivial rebases prior to submitting a change. Defaults to false.

[[label_copyAllScoresIfNoCodeChange]]
=== `label.Label-Name.copyAllScoresIfNoCodeChange`

If true, all scores for the label are copied forward when a new patch
set is uploaded that has the same parent commit as the previous patch
set and the same code delta as the previous patch set. This means only
the commit message is different. This can be used to enable sticky
approvals on labels that only depend on the code, reducing turn-around
if only the commit message is changed prior to submitting a change.
Defaults to false.

[[label_canOverride]]
=== `label.Label-Name.canOverride`

If false, the label cannot be overridden by child projects. Any
configuration for this label in child projects will be ignored. Defaults
to true.

[[label_branch]]
=== `label.Label-Name.branch`

By default a given project's label applicable scope is all changes
on all branches of this project and its child projects.

Label's applicable scope can be branch specific via configuration.
E.g. create a label `Video-Qualify` on parent project and configure
the `branch` as:

====
  [label "Video-Qualify"]
      branch = refs/heads/video-1.0/*
      branch = refs/heads/video-1.1/Kino
====

Then *only* changes in above branch scope of parent project and child
projects will be affected by `Video-Qualify`.

NOTE: The `branch` is independent from the branch scope defined in `access`
parts in `project.config` file. That means from the UI a user can always
assign permissions for that label on a branch, but this permission is then
ignored if the label doesn't apply for that branch.

[[label_example]]
=== Example

To define a new 3-valued category that behaves exactly like `Verified`,
but has different names/labels:

====
  [label "Copyright-Check"]
      function = MaxWithBlock
      value = -1 Do not have copyright
      value =  0 No score
      value = +1 Copyright clear
====

The new column will appear at the end of the table, and `-1 Do not have
copyright` will block submit, while `+1 Copyright clear` is required to
enable submit.

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