Documentation/intro-gerrit-walkthrough.txt - gerrit - Git at Google

 :linkattrs:
 = Working with Gerrit: An example

 To understand how Gerrit works, let's follow a change through its entire
 life cycle. This example uses a Gerrit server configured as follows:

 * *Hostname*: gerrithost
 * *HTTP interface port*: 80
 * *SSH interface port*: 29418

 In this walkthrough, we'll follow two developers, Max and Hannah, as they make
 and review a change to a +RecipeBook+ project. We'll follow the change through
 these stages:

 . Making the change.
 . Creating the review.
 . Reviewing the change.
 . Reworking the change.
 . Verifying the change.
 . Submitting the change.

 NOTE: The project and commands used in this section are for demonstration
 purposes only.

 == Making the Change

 Our first developer, Max, has decided to make a change to the +RecipeBook+
 project he works on. His first step is to get the source code that he wants to
 modify. To get this code, he runs the following `git clone` command:

 ----
 git clone ssh://gerrithost:29418/RecipeBook.git RecipeBook
 ----

 After he clones the repository, he runs a couple of commands to add a
 link:user-changeid.html[Change-Id] to his commits. This ID allows Gerrit to link
 together different versions of the same change being reviewed.

 ....
 scp -p -P 29418 gerrithost:hooks/commit-msg RecipeBook/.git/hooks/
 chmod u+x .git/hooks/commit-msg
 ....

 NOTE: To learn more about adding a change-id and the commit message hook, see
 the link:cmd-hook-commit-msg.html[commit-msg Hook] topic.

 == Creating the Review

 Max's next step is to push his change to Gerrit so other contributors can review
 it. He does this using the `git push origin HEAD:refs/for/master` command, as
 follows:

 ----
 $ <work>
 $ git commit
 [master 3cc9e62] Change to a proper, yeast based pizza dough.
  1 file changed, 10 insertions(+), 5 deletions(-)
 $ git push origin HEAD:refs/for/master
 Counting objects: 3, done.
 Delta compression using up to 8 threads.
 Compressing objects: 100% (2/2), done.
 Writing objects: 100% (3/3), 532 bytes | 0 bytes/s, done.
 Total 3 (delta 0), reused 0 (delta 0)
 remote: Processing changes: new: 1, done
 remote:
 remote: New Changes:
 remote:   http://gerrithost/#/c/RecipeBook/+/702 Change to a proper, yeast based pizza dough.
 remote:
 To ssh://gerrithost:29418/RecipeBook
  * [new branch]      HEAD -> refs/for/master
 ----

 Notice the reference to a `refs/for/master` branch. Gerrit uses this branch to
 create reviews for the master branch. If Max opted to push to a different
 branch, he would have modified his command to
 `git push origin HEAD:refs/for/<branch_name>`. Gerrit accepts pushes to
 `refs/for/<branch_name>` for every branch that it tracks.

 The output of this command also contains a link to a web page Max can use to
 review this commit. Clicking on that link takes him to a screen similar to
 the following.

 .Gerrit Code Review Screen
 image::images/intro-quick-new-review.png[Gerrit Review Screen]

 This is the Gerrit code review screen, where other contributors can review
 his change. Max can also perform tasks such as:

 * Looking at the link:user-review-ui.html#diff-preferences[diff] of his change
 * Writing link:user-review-ui.html#inline-comments[inline] or
   link:user-review-ui.html#reply[summary] comments to ask reviewers for advice
   on particular aspects of the change
 * link:intro-user.html#adding-reviewers[Adding a list of people] that should
   review the change

 In this case, Max opts to manually add the senior developer on his team, Hannah,
 to review his change.

 == Reviewing the Change

 Let's now switch to Hannah, the senior developer who will review Max's change.

 As mentioned previously, Max chose to manually add Hannah as a reviewer. Gerrit
 offers other ways for reviewers to find changes, including:

 * Using the link:user-search.html[search] feature that to find changes
 * Selecting *Open* from the *Changes* menu
 * Setting up link:user-notify.html[email notifications] to stay informed of
   changes even if you are not added as a reviewer

 Because Max added Hannah as a reviewer, she receives an email telling her about
 his change. She opens up the Gerrit code review screen and selects Max's change.

 Notice the *Label status* section above:

 ----
 Label Status Needs label:
              * Code-Review
              * Verified
 ----

 These two lines indicate what checks must be completed before the change is
 accepted. The default Gerrit workflow requires two checks:

 * *Code-Review*. This check requires that someone look at the code and ensures
   that it meets project guidelines, styles, and other criteria.
 * *Verified*. This check means that the code actually compiles, passes any unit
   tests, and performs as expected.

 In general, the *Code-Review* check requires an individual to look at the code,
 while the *Verified* check is done by an automated build server, through a
 mechanism such as the
 link:https://plugins.jenkins.io/gerrit-trigger/[Gerrit Trigger
 Jenkins Plugin,role=external,window=_blank].

 IMPORTANT: The Code-Review and Verified checks require different permissions
 in Gerrit. This requirement allows teams to separate these tasks. For example,
 an automated process can have the rights to verify a change, but not perform a
 code review.

 With the code review screen open, Hannah can begin to review Max's change. She
 can choose one of two ways to review the change: unified or side-by-side.
 Both views allow her to perform tasks such as add
 link:user-review-ui.html#inline-comments[inline] or
 link:user-review-ui.html#reply[summary] comments.

 Hannah opts to view the change using Gerrit's side-by-side view:

 .Side By Side Patch View
 image::images/intro-quick-review-line-comment.png[Adding a Comment]

 Hannah reviews the change and is ready to provide her feedback. She clicks the
 *REPLY* button on the change screen. This allows her to vote on the change.

 .Reviewing the Change
 image::images/intro-quick-reviewing-the-change.png[Reviewing the Change]

 For Hannah and Max's team, a code review vote is a numerical score between -2
 and 2. The possible options are:

 * `+2 Looks good to me, approved`
 * `+1 Looks good to me, but someone else must approve`
 * `0 No score`
 * `-1 I would prefer this is not submitted as is`
 * `-2 This shall not be submitted`

 In addition, a change must have at least one `+2` vote and no `-2` votes before
 it can be submitted. These numerical values do not accumulate. Two
 `+1` votes do not equate to a `+2`.

 NOTE: These settings are enabled by default. To learn about how to customize
 them for your own workflow, see the
 link:config-project-config.html[Project Configuration File Format] topic.

 Hannah notices a possible issue with Max's change, so she selects a `-1` vote.
 She uses the *Cover Message* text box to provide Max with some additional
 feedback. When she is satisfied with her review, Hannah clicks the
 *SEND* button. At this point, her vote and cover message become
 visible to to all users.

 == Reworking the Change

 Later in the day, Max decides to check on his change and notices Hannah's
 feedback. He opens up the source file and incorporates her feedback. Because
 Max's change includes a change-id, all he has to do is follow the typical git
 workflow for updating a commit:

 * Check out the commit
 * Amend the commit
 * Rebase the commit if needed
 * Push the commit to Gerrit

 ----
 $ <checkout first commit>
 $ <rework>
 $ git commit --amend
 [master 30a6f44] Change to a proper, yeast based pizza dough.
  Date: Fri Jun 8 16:28:23 2018 +0200
  1 file changed, 10 insertions(+), 5 deletions(-)
 ----

 At this point Max wants to make sure that his change is on top of the branch.

 ----
 $ git fetch
 $
 ----

 Max got no output from the fetch command, which is good news.
 This means that the master branch has not progressed and there is no need for link:intro-user.html#rebase[*rebase*].
 Max is now ready to push his change:

 ----
 $ git push origin HEAD:refs/for/master
 Counting objects: 3, done.
 Delta compression using up to 8 threads.
 Compressing objects: 100% (2/2), done.
 Writing objects: 100% (3/3), 528 bytes | 0 bytes/s, done.
 Total 3 (delta 0), reused 0 (delta 0)
 remote: Processing changes: updated: 1, done
 remote:
 remote: Updated Changes:
 remote:   http://gerrithost/#/c/RecipeBook/+/702 Change to a proper, yeast based pizza dough.
 remote:
 To ssh://gerrithost:29418/RecipeBook
  * [new branch]      HEAD -> refs/for/master
 ----

 Notice that the output of this command is slightly different from Max's first
 commit. This time, the output verifies that the change was updated.

 Having uploaded the reworked commit, Max can go back to the Gerrit web
 interface, look at his change and diff the first patch set with his rework in
 the second one. Once he has verified that the rework follows Hannahs
 recommendation he presses the *DONE* button to let Hannah know that she can
 review the changes.

 When Hannah next looks at Max's change, she sees that he incorporated her
 feedback. The change looks good to her, so she changes her vote to a `+2`.

 == Verifying the Change

 Hannah's `+2` vote means that Max's change satisfies the *Needs Review*
 check. It has to pass one more check before it can be accepted: the *Needs
 Verified* check.

 The Verified check means that the change was confirmed to work. This type of
 check typically involves tasks such as checking that the code compiles, unit
 tests pass, and other actions. You can configure a Verified check to consist
 of as many or as few tasks as needed.

 NOTE: Remember that this walkthrough uses Gerrit's default workflow. Projects
 can add custom checks or even remove the Verified check entirely.

 Verification is typically an automated process using the
 link:https://plugins.jenkins.io/gerrit-trigger/[Gerrit Trigger Jenkins Plugin,role=external,window=_blank]
 or a similar mechanism. However, there are still times when a change requires
 manual verification, or a reviewer needs to check how or if a change works.
 To accommodate these and other similar circumstances, Gerrit exposes each change
 as a git branch. The Gerrit UI includes a
 link:user-review-us.html#download[*download*] link in the Gerrit Code Review
 Screen to make it easy for reviewers to fetch a branch for a specific change.
 To manually verify a change, a reviewer must have the
 link:config-labels.html#label_Verified[Verified] permission. Then, the reviewer
 can fetch and checkout that branch from Gerrit. Hannah has this permission, so
 she is authorized to manually verify Max's change.

 NOTE: The Verifier can be the same person as the code reviewer or a
 different person entirely.

 .Verifying the Change
 image::images/intro-quick-verifying.png[Verifying the Change]

 Unlike the code review check, the verify check is pass/fail. Hannah can provide
 a score of either `+1` or `-1`. A change must have at least one `+1` and no
 `-1`.

 Hannah selects a `+1` for her verified check. Max's change is now ready to be
 submitted.

 == Submitting the Change

 Max is now ready to submit his change. He opens up the change in the Code Review
 screen and clicks the *SUBMIT* button.

 At this point, Max's change is merged into the repository's master branch and
 becomes an accepted part of the project.

 == Next Steps

 This walkthrough provided a quick overview of how a change moves
 through the default Gerrit workflow. At this point, you can:

 * Read the link:intro-user.html[Users guide] to get a better sense of how to
   make changes using Gerrit
 * Review the link:intro-project-owner.html[Project Owners guide] to learn more
   about configuring projects in Gerrit, including setting user permissions and
   configuring verification checks
 * Read through the Git and Gerrit training slides that explain concepts and
   workflows in detail. They are meant for self-studying how Git and Gerrit work:
 ** link:https://docs.google.com/presentation/d/1IQCRPHEIX-qKo7QFxsD3V62yhyGA9_5YsYXFOiBpgkk/edit?usp=sharing[Git explained: Git Concepts and Workflows]
 ** link:https://docs.google.com/presentation/d/1C73UgQdzZDw0gzpaEqIC6SPujZJhqamyqO1XOHjH-uk/edit?usp=sharing[Gerrit explained: Gerrit Concepts and Workflows]

 GERRIT
 ------
 Part of link:index.html[Gerrit Code Review]

 SEARCHBOX
 ---------
	:linkattrs:
	= Working with Gerrit: An example

	To understand how Gerrit works, let's follow a change through its entire
	life cycle. This example uses a Gerrit server configured as follows:

	* Hostname: gerrithost
	* HTTP interface port: 80
	* SSH interface port: 29418

	In this walkthrough, we'll follow two developers, Max and Hannah, as they make
	and review a change to a +RecipeBook+ project. We'll follow the change through
	these stages:

	. Making the change.
	. Creating the review.
	. Reviewing the change.
	. Reworking the change.
	. Verifying the change.
	. Submitting the change.

	NOTE: The project and commands used in this section are for demonstration
	purposes only.

	== Making the Change

	Our first developer, Max, has decided to make a change to the +RecipeBook+
	project he works on. His first step is to get the source code that he wants to
	modify. To get this code, he runs the following `git clone` command:

	----
	git clone ssh://gerrithost:29418/RecipeBook.git RecipeBook
	----

	After he clones the repository, he runs a couple of commands to add a
	link:user-changeid.html[Change-Id] to his commits. This ID allows Gerrit to link
	together different versions of the same change being reviewed.

	....
	scp -p -P 29418 gerrithost:hooks/commit-msg RecipeBook/.git/hooks/
	chmod u+x .git/hooks/commit-msg
	....

	NOTE: To learn more about adding a change-id and the commit message hook, see
	the link:cmd-hook-commit-msg.html[commit-msg Hook] topic.

	== Creating the Review

	Max's next step is to push his change to Gerrit so other contributors can review
	it. He does this using the `git push origin HEAD:refs/for/master` command, as
	follows:

	----
	$ <work>
	$ git commit
	[master 3cc9e62] Change to a proper, yeast based pizza dough.
	1 file changed, 10 insertions(+), 5 deletions(-)
	$ git push origin HEAD:refs/for/master
	Counting objects: 3, done.
	Delta compression using up to 8 threads.
	Compressing objects: 100% (2/2), done.
	Writing objects: 100% (3/3), 532 bytes \| 0 bytes/s, done.
	Total 3 (delta 0), reused 0 (delta 0)
	remote: Processing changes: new: 1, done
	remote:
	remote: New Changes:
	remote: http://gerrithost/#/c/RecipeBook/+/702 Change to a proper, yeast based pizza dough.
	remote:
	To ssh://gerrithost:29418/RecipeBook
	* [new branch] HEAD -> refs/for/master
	----

	Notice the reference to a `refs/for/master` branch. Gerrit uses this branch to
	create reviews for the master branch. If Max opted to push to a different
	branch, he would have modified his command to
	`git push origin HEAD:refs/for/<branch_name>`. Gerrit accepts pushes to
	`refs/for/<branch_name>` for every branch that it tracks.

	The output of this command also contains a link to a web page Max can use to
	review this commit. Clicking on that link takes him to a screen similar to
	the following.

	.Gerrit Code Review Screen
	image::images/intro-quick-new-review.png[Gerrit Review Screen]

	This is the Gerrit code review screen, where other contributors can review
	his change. Max can also perform tasks such as:

	* Looking at the link:user-review-ui.html#diff-preferences[diff] of his change
	* Writing link:user-review-ui.html#inline-comments[inline] or
	link:user-review-ui.html#reply[summary] comments to ask reviewers for advice
	on particular aspects of the change
	* link:intro-user.html#adding-reviewers[Adding a list of people] that should
	review the change

	In this case, Max opts to manually add the senior developer on his team, Hannah,
	to review his change.

	== Reviewing the Change

	Let's now switch to Hannah, the senior developer who will review Max's change.

	As mentioned previously, Max chose to manually add Hannah as a reviewer. Gerrit
	offers other ways for reviewers to find changes, including:

	* Using the link:user-search.html[search] feature that to find changes
	* Selecting Open from the Changes menu
	* Setting up link:user-notify.html[email notifications] to stay informed of
	changes even if you are not added as a reviewer

	Because Max added Hannah as a reviewer, she receives an email telling her about
	his change. She opens up the Gerrit code review screen and selects Max's change.

	Notice the Label status section above:

	----
	Label Status Needs label:
	* Code-Review
	* Verified
	----

	These two lines indicate what checks must be completed before the change is
	accepted. The default Gerrit workflow requires two checks:

	* Code-Review. This check requires that someone look at the code and ensures
	that it meets project guidelines, styles, and other criteria.
	* Verified. This check means that the code actually compiles, passes any unit
	tests, and performs as expected.

	In general, the Code-Review check requires an individual to look at the code,
	while the Verified check is done by an automated build server, through a
	mechanism such as the
	link:https://plugins.jenkins.io/gerrit-trigger/[Gerrit Trigger
	Jenkins Plugin,role=external,window=_blank].

	IMPORTANT: The Code-Review and Verified checks require different permissions
	in Gerrit. This requirement allows teams to separate these tasks. For example,
	an automated process can have the rights to verify a change, but not perform a
	code review.

	With the code review screen open, Hannah can begin to review Max's change. She
	can choose one of two ways to review the change: unified or side-by-side.
	Both views allow her to perform tasks such as add
	link:user-review-ui.html#inline-comments[inline] or
	link:user-review-ui.html#reply[summary] comments.

	Hannah opts to view the change using Gerrit's side-by-side view:

	.Side By Side Patch View
	image::images/intro-quick-review-line-comment.png[Adding a Comment]

	Hannah reviews the change and is ready to provide her feedback. She clicks the
	REPLY button on the change screen. This allows her to vote on the change.

	.Reviewing the Change
	image::images/intro-quick-reviewing-the-change.png[Reviewing the Change]

	For Hannah and Max's team, a code review vote is a numerical score between -2
	and 2. The possible options are:

	* `+2 Looks good to me, approved`
	* `+1 Looks good to me, but someone else must approve`
	* `0 No score`
	* `-1 I would prefer this is not submitted as is`
	* `-2 This shall not be submitted`

	In addition, a change must have at least one `+2` vote and no `-2` votes before
	it can be submitted. These numerical values do not accumulate. Two
	`+1` votes do not equate to a `+2`.

	NOTE: These settings are enabled by default. To learn about how to customize
	them for your own workflow, see the
	link:config-project-config.html[Project Configuration File Format] topic.

	Hannah notices a possible issue with Max's change, so she selects a `-1` vote.
	She uses the Cover Message text box to provide Max with some additional
	feedback. When she is satisfied with her review, Hannah clicks the
	SEND button. At this point, her vote and cover message become
	visible to to all users.

	== Reworking the Change

	Later in the day, Max decides to check on his change and notices Hannah's
	feedback. He opens up the source file and incorporates her feedback. Because
	Max's change includes a change-id, all he has to do is follow the typical git
	workflow for updating a commit:

	* Check out the commit
	* Amend the commit
	* Rebase the commit if needed
	* Push the commit to Gerrit

	----
	$ <checkout first commit>
	$ <rework>
	$ git commit --amend
	[master 30a6f44] Change to a proper, yeast based pizza dough.
	Date: Fri Jun 8 16:28:23 2018 +0200
	1 file changed, 10 insertions(+), 5 deletions(-)
	----

	At this point Max wants to make sure that his change is on top of the branch.

	----
	$ git fetch
	$
	----

	Max got no output from the fetch command, which is good news.
	This means that the master branch has not progressed and there is no need for link:intro-user.html#rebase[rebase].
	Max is now ready to push his change:

	----
	$ git push origin HEAD:refs/for/master
	Counting objects: 3, done.
	Delta compression using up to 8 threads.
	Compressing objects: 100% (2/2), done.
	Writing objects: 100% (3/3), 528 bytes \| 0 bytes/s, done.
	Total 3 (delta 0), reused 0 (delta 0)
	remote: Processing changes: updated: 1, done
	remote:
	remote: Updated Changes:
	remote: http://gerrithost/#/c/RecipeBook/+/702 Change to a proper, yeast based pizza dough.
	remote:
	To ssh://gerrithost:29418/RecipeBook
	* [new branch] HEAD -> refs/for/master
	----

	Notice that the output of this command is slightly different from Max's first
	commit. This time, the output verifies that the change was updated.

	Having uploaded the reworked commit, Max can go back to the Gerrit web
	interface, look at his change and diff the first patch set with his rework in
	the second one. Once he has verified that the rework follows Hannahs
	recommendation he presses the DONE button to let Hannah know that she can
	review the changes.

	When Hannah next looks at Max's change, she sees that he incorporated her
	feedback. The change looks good to her, so she changes her vote to a `+2`.

	== Verifying the Change

	Hannah's `+2` vote means that Max's change satisfies the Needs Review
	check. It has to pass one more check before it can be accepted: the *Needs
	Verified* check.

	The Verified check means that the change was confirmed to work. This type of
	check typically involves tasks such as checking that the code compiles, unit
	tests pass, and other actions. You can configure a Verified check to consist
	of as many or as few tasks as needed.

	NOTE: Remember that this walkthrough uses Gerrit's default workflow. Projects
	can add custom checks or even remove the Verified check entirely.

	Verification is typically an automated process using the
	link:https://plugins.jenkins.io/gerrit-trigger/[Gerrit Trigger Jenkins Plugin,role=external,window=_blank]
	or a similar mechanism. However, there are still times when a change requires
	manual verification, or a reviewer needs to check how or if a change works.
	To accommodate these and other similar circumstances, Gerrit exposes each change
	as a git branch. The Gerrit UI includes a
	link:user-review-us.html#download[download] link in the Gerrit Code Review
	Screen to make it easy for reviewers to fetch a branch for a specific change.
	To manually verify a change, a reviewer must have the
	link:config-labels.html#label_Verified[Verified] permission. Then, the reviewer
	can fetch and checkout that branch from Gerrit. Hannah has this permission, so
	she is authorized to manually verify Max's change.

	NOTE: The Verifier can be the same person as the code reviewer or a
	different person entirely.

	.Verifying the Change
	image::images/intro-quick-verifying.png[Verifying the Change]

	Unlike the code review check, the verify check is pass/fail. Hannah can provide
	a score of either `+1` or `-1`. A change must have at least one `+1` and no
	`-1`.

	Hannah selects a `+1` for her verified check. Max's change is now ready to be
	submitted.

	== Submitting the Change

	Max is now ready to submit his change. He opens up the change in the Code Review
	screen and clicks the SUBMIT button.

	At this point, Max's change is merged into the repository's master branch and
	becomes an accepted part of the project.

	== Next Steps

	This walkthrough provided a quick overview of how a change moves
	through the default Gerrit workflow. At this point, you can:

	* Read the link:intro-user.html[Users guide] to get a better sense of how to
	make changes using Gerrit
	* Review the link:intro-project-owner.html[Project Owners guide] to learn more
	about configuring projects in Gerrit, including setting user permissions and
	configuring verification checks
	* Read through the Git and Gerrit training slides that explain concepts and
	workflows in detail. They are meant for self-studying how Git and Gerrit work:
	** link:https://docs.google.com/presentation/d/1IQCRPHEIX-qKo7QFxsD3V62yhyGA9_5YsYXFOiBpgkk/edit?usp=sharing[Git explained: Git Concepts and Workflows]
	** link:https://docs.google.com/presentation/d/1C73UgQdzZDw0gzpaEqIC6SPujZJhqamyqO1XOHjH-uk/edit?usp=sharing[Gerrit explained: Gerrit Concepts and Workflows]

	GERRIT
	------
	Part of link:index.html[Gerrit Code Review]

	SEARCHBOX
	---------