Documentation/user-upload.txt - gerrit - Git at Google

 Gerrit Code Review - Uploading Changes
 ======================================

 Gerrit supports three methods of uploading changes:

 * Use `repo upload`, to create changes for review
 * Use `git push`, to create changes for review
 * Use `git push`, and bypass code review

 All three methods rely on authentication, which must first be configured
 by the uploading user.

 Gerrit supports two methods of authenticating the uploading user.  SSH
 public key, and HTTP/HTTPS.

 [[http]]
 HTTP/HTTPS
 ----------

 On Gerrit installations that do not support SSH authentication, the
 user must authenticate via HTTP/HTTPS.

 When link:config-gerrit.html#auth.gitBasicAuth[gitBasicAuth] is enabled,
 the user is authenticated using standard BasicAuth and credentials validated
 using the same authentication method configured for the Gerrit Web UI.

 When gitBasicAuth is not configured, the user's HTTP credentials can be
 accessed within Gerrit by going to `Settings`, and then accessing the `HTTP
 Password` tab.

 For Gerrit installations where an link:config-gerrit.html#auth.httpPasswordUrl[HTTP password URL]
 is configured, the password can be obtained by clicking on `Obtain Password`
 and then following the site-specific instructions.  On sites where this URL is
 not configured, the password can be obtained by clicking on `Generate Password`.

 SSH
 ---

 Each user uploading changes to Gerrit must configure one or more SSH
 public keys.  The per-user SSH key list can be accessed over the web
 within Gerrit by `Settings`, and then accessing the `SSH Public Keys`
 tab.

 [[configure_ssh]]
 Configuration
 ~~~~~~~~~~~~~

 To register a new SSH key for use with Gerrit, paste the contents of
 your `id_rsa.pub` or `id_dsa.pub` file into the text box and click
 the add button.  Gerrit only understands SSH version 2 public keys.
 Keys may be supplied in either the OpenSSH format (key starts with
 `ssh-rsa` or `ssh-dss`) or the RFC 4716 format (file starts with
 `---- BEGIN SSH2 PUBLIC KEY ----`).

 Typically SSH keys are stored in your home directory, under `~/.ssh`.
 If you don't have any keys yet, you can create a new one and protect
 it with a passphrase:

 ====
   ssh-keygen -t rsa
 ====

 Then copy the content of the public key file onto your clipboard,
 and paste it into Gerrit's web interface:

 ====
   cat ~/.ssh/id_rsa.pub
 ====

 [TIP]
 Users who frequently upload changes will also want to consider
 starting an `ssh-agent`, and adding their private key to the list
 managed by the agent, to reduce the frequency of entering the
 key's passphrase.  Consult `man ssh-agent`, or your SSH client's
 documentation, for more details on configuration of the agent
 process and how to add the private key.

 [[test_ssh]]
 Testing Connections
 ~~~~~~~~~~~~~~~~~~~

 To verify your SSH key is working correctly, try using an SSH client
 to connect to Gerrit's SSHD port.  By default Gerrit runs on
 port 29418, using the same hostname as the web server:

 ====
 ..................................................................
   $ ssh -p 29418 sshusername@hostname

     ****    Welcome to Gerrit Code Review    ****

     Hi John Doe, you have successfully connected over SSH.

     Unfortunately, interactive shells are disabled.
     To clone a hosted Git repository, use:

     git clone ssh://sshusername@hostname:29418/REPOSITORY_NAME.git

   Connection to hostname closed.
 ..................................................................
 ====

 In the command above, `sshusername` was configured as `Username` on
 the `Profile` tab of the `Settings` screen.  If it is not set,
 propose a name and use `Select Username` to select the name.

 To determine the port number Gerrit is running on, visit the special
 information URL `http://'hostname'/ssh_info`, and copy the port
 number from the second field:

 ====
   $ curl http://hostname/ssh_info
   hostname 29418
 ====

 If you are developing an automated tool to perform uploads to Gerrit,
 let the user supply the hostname or the web address for Gerrit,
 and obtain the port number on the fly from the `/ssh_info` URL.
 The returned output from this URL is always `'hostname' SP 'port'`,
 or `NOT_AVAILABLE` if the SSHD server is not currently running.


 git push
 --------

 [[push_create]]
 Create Changes
 ~~~~~~~~~~~~~~

 To create new changes for review, simply push to the project's
 magical `refs/for/'branch'` ref using any Git client tool:

 ====
   git push ssh://sshusername@hostname:29418/projectname HEAD:refs/for/branch
 ====

 E.g. `john.doe` can use git push to upload new changes for the
 `experimental` branch of project `kernel/common`, hosted at the
 `git.example.com` Gerrit server:

 ====
   git push ssh://john.doe@git.example.com:29418/kernel/common HEAD:refs/for/experimental
 ====

 Each new commit uploaded by the `git push` client will be
 converted into a change record on the server.  The remote ref
 `refs/for/experimental` is not actually created by Gerrit, even
 though the client's status messages may say otherwise.

 Other users (e.g. project owners) who have configured Gerrit to
 notify them of new changes will be automatically sent an email
 message when the push is completed.

 To include a short tag associated with all of the changes in the
 same group, such as the local topic branch name, append it after
 the destination branch name. In this example the short topic tag
 'driver/i42' will be saved on each change this push creates or
 updates:

 ====
   git push ssh://john.doe@git.example.com:29418/kernel/common HEAD:refs/for/experimental%topic=driver/i42
 ====

 If you are frequently uploading changes to the same Gerrit server,
 consider adding an SSH host block in `~/.ssh/config` to remember
 your username, hostname and port number.  This permits the use of
 shorter URLs on the command line, such as:

 ====
   $ cat ~/.ssh/config
   ...
   Host tr
     Hostname git.example.com
     Port 29418
     User john.doe

   $ git push tr:kernel/common HEAD:refs/for/experimental
 ====

 Specific reviewers can be requested and/or additional 'carbon
 copies' of the notification message may be sent by including these
 as options in the reference

 ====
   git push tr:kernel/common HEAD:refs/for/experimental%r=a@a.com,cc=b@o.com
 ====

 The `r='email'` and `cc='email'` options may be specified as many
 times as necessary to cover all interested parties. Gerrit will
 automatically avoid sending duplicate email notifications, such as
 if one of the specified reviewers or CC addresses had also requested
 to receive all new change notifications.

 If you are frequently sending changes to the same parties and/or
 branches, consider adding a custom remote block to your project's
 `.git/config` file:

 ====
   $ cat .git/config
   ...
   [remote "exp"]
     url = tr:kernel/common
     push = HEAD:refs/for/experimental%r=a@a.com,cc=b@o.com

   $ git push exp
 ====


 [[push_replace]]
 Replace Changes
 ~~~~~~~~~~~~~~~

 To add an additional patch set to a change, ensure Change-Id
 lines were created in the original commit messages, and just use
 `git push URL HEAD:refs/for/...` as <<push_create,described above>>.
 Gerrit Code Review will automatically match the commits back to
 their original changes by taking advantage of the Change-Id lines.

 If Change-Id lines are not present in the commit messages, consider
 amending the message and copying the line from the change's page
 on the web, and then using `git push` as described above.

 If Change-Id lines are not available, then the user must use the
 manual mapping technique described below.

 For more about Change-Ids, see link:user-changeid.html[Change-Id Lines].

 [[manual_replacement_mapping]]
 Manual Replacement Mapping
 ^^^^^^^^^^^^^^^^^^^^^^^^^^

 .Deprecation Warning
 ****
 The remainder of this section describes a manual method of replacing
 changes by matching each commit name to an existing change number.
 End-users should instead prefer to use Change-Id lines in their
 commit messages, as the process is then fully automated by Gerrit
 during normal uploads.

 See above for the preferred technique of replacing changes.
 ****

 To add an additional patch set to a change, replacing it with an
 updated version of the same logical modification, send the new
 commit to the change's ref.  For example, to add the commit whose
 SHA-1 starts with `c0ffee` as a new patch set for change number
 `1979`, use the push refspec `c0ffee:refs/changes/1979` as below:

 ====
   git push ssh://sshusername@hostname:29418/projectname c0ffee:refs/changes/1979
 ====

 This form can be combined together with `refs/for/'branchname'`
 (above) to simultaneously create new changes and replace changes
 during one network transaction.

 For example, consider the following sequence of events:

 ====
   $ git commit -m A                    ; # create 3 commits
   $ git commit -m B
   $ git commit -m C

   $ git push ... HEAD:refs/for/master  ; # upload for review
   ... A is 1500 ...
   ... B is 1501 ...
   ... C is 1502 ...

   $ git rebase -i HEAD~3               ; # edit "A", insert D before B
                                        ; # now series is A'-D-B'-C'
   $ git push ...
       HEAD:refs/for/master
       HEAD~3:refs/changes/1500
       HEAD~1:refs/changes/1501
       HEAD~0:refs/changes/1502         ; # upload replacements
 ====

 At the final step during the push Gerrit will attach A' as a new
 patch set on change 1500; B' as a new patch set on change 1501; C'
 as a new patch set on 1502; and D will be created as a new change.

 Ensuring D is created as a new change requires passing the refspec
 `HEAD:refs/for/branchname`, otherwise Gerrit will ignore D and
 won't do anything with it.  For this reason it is a good idea to
 always include the create change refspec when uploading replacements.


 [[bypass_review]]
 Bypass Review
 ~~~~~~~~~~~~~

 Changes (and annotated tags) can be pushed directly into a
 repository, bypassing the review process.  This is primarily useful
 for a project owner to create new branches, create annotated tags
 for releases, or to force-update a branch whose history needed to
 be rewritten.

 Gerrit restricts direct pushes that bypass review to:

 * `refs/heads/*`: any branch can be updated, created, deleted,
 or rewritten by the pusher.
 * `refs/tags/*`: annotated tag objects pointing to any other type
 of Git object can be created.

 To push branches, the proper access rights must be configured first.
 Here follows a few examples of how to configure this in Gerrit:

 * Update: Any existing branch can be fast-forwarded to a new commit.
 This is the safest mode as commits cannot be discarded.  Creation
 of new branches is rejected. Can be configured with
 link:access-control.html#category_push_direct['Push'] access.
 * Create: Allows creation of a new branch if the name does not
 already designate an existing branch name.  Needs
 link:access-control.html#category_create['Create Reference']
 configured. Please note that once created, this permission doesn't
 grant the right to update the branch with further commits (see above
 for update details).
 * Delete: Implies Update, but also allows an existing
 branch to be deleted.  Since a force push is effectively a delete
 followed by a create, but performed atomically on the server and
 logged, this also permits forced push updates to branches.
 To grant this access, configure
 link:access-control.html#category_push_direct['Push'] with the
 'Force' option ticked.

 To push annotated tags, the `Push Annotated Tag` project right must
 be granted to one (or more) of the user's groups.  There is only
 one level of access in this category.

 Project owners may wish to grant themselves `Push Annotated Tag`
 only at times when a new release is being prepared, and otherwise
 grant nothing at all.  This ensures that accidental pushes don't
 make undesired changes to the public repository.


 repo upload
 -----------

 repo is a multiple repository management tool, most commonly
 used by the Android Open Source Project.  For more details, see
 link:http://source.android.com/source/using-repo.html[using repo].

 [[repo_create]]
 Create Changes
 ~~~~~~~~~~~~~~

 To upload changes to a project using `repo`, ensure the manifest's
 review field has been configured to point to the Gerrit server.
 Only the hostname or the web address needs to be given in the
 manifest file. During upload `repo` will automatically determine the
 correct port number by reading `http://'reviewhostname'/ssh_info`
 when its invoked.

 Each new commit uploaded by `repo upload` will be converted into
 a change record on the server.  Other users (e.g. project owners)
 who have configured Gerrit to notify them of new changes will be
 automatically sent an email message.  Additional notifications can
 be sent through command line options.

 For more details on using `repo upload`, see `repo help upload`.

 [[repo_replace]]
 Replace Changes
 ~~~~~~~~~~~~~~~

 To replace changes, ensure Change-Id lines were created in the
 commit messages, and just use `repo upload`.
 Gerrit Code Review will automatically match the commits back to
 their original changes by taking advantage of their Change-Id lines.

 If Change-Id lines are not present in the commit messages, consider
 amending the message and copying the line from the change's page
 on the web.

 If Change-Id lines are not available, then the user must use the much
 more <<manual_replacement_mapping,manual mapping technique>> offered
 by using `git push` to a specific `refs/changes/change#` reference.

 For more about Change-Ids, see link:user-changeid.html[Change-Id Lines].


 Gritty Details
 --------------

 As Gerrit implements the entire SSH and Git server stack within its
 own process space, Gerrit maintains complete control over how the
 repository is updated, and what responses are sent to the `git push`
 client invoked by the end-user, or by `repo upload`.  This allows
 Gerrit to provide magical refs, such as `refs/for/*` for new
 change submission and `refs/changes/*` for change replacement.
 When a push request is received to create a ref in one of these
 namespaces Gerrit performs its own logic to update the database,
 and then lies to the client about the result of the operation.
 A successful result causes the client to believe that Gerrit has
 created the ref, but in reality Gerrit hasn't created the ref at all.

 By implementing the entire server stack, Gerrit is also able to
 perform project level access control checks (to verify the end-user
 is permitted to access a project) prior to advertising the available
 refs, and potentially leaking information to a snooping client.
 Clients cannot tell the difference between 'project not found' and
 'project exists, but access is denied'.

 Gerrit can also ensure users have completed a valid Contributor
 Agreement prior to accepting any transferred objects, and if an
 agreement is required, but not completed, it aborts the network
 connection before data is sent.  This ensures that project owners
 can be certain any object available in their repository has been
 supplied under at least one valid agreement.

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

	Gerrit supports three methods of uploading changes:

	* Use `repo upload`, to create changes for review
	* Use `git push`, to create changes for review
	* Use `git push`, and bypass code review

	All three methods rely on authentication, which must first be configured
	by the uploading user.

	Gerrit supports two methods of authenticating the uploading user. SSH
	public key, and HTTP/HTTPS.

	[[http]]
	HTTP/HTTPS
	----------

	On Gerrit installations that do not support SSH authentication, the
	user must authenticate via HTTP/HTTPS.

	When link:config-gerrit.html#auth.gitBasicAuth[gitBasicAuth] is enabled,
	the user is authenticated using standard BasicAuth and credentials validated
	using the same authentication method configured for the Gerrit Web UI.

	When gitBasicAuth is not configured, the user's HTTP credentials can be
	accessed within Gerrit by going to `Settings`, and then accessing the `HTTP
	Password` tab.

	For Gerrit installations where an link:config-gerrit.html#auth.httpPasswordUrl[HTTP password URL]
	is configured, the password can be obtained by clicking on `Obtain Password`
	and then following the site-specific instructions. On sites where this URL is
	not configured, the password can be obtained by clicking on `Generate Password`.

	SSH
	---

	Each user uploading changes to Gerrit must configure one or more SSH
	public keys. The per-user SSH key list can be accessed over the web
	within Gerrit by `Settings`, and then accessing the `SSH Public Keys`
	tab.

	[[configure_ssh]]
	Configuration
	~~~~~~~~~~~~~

	To register a new SSH key for use with Gerrit, paste the contents of
	your `id_rsa.pub` or `id_dsa.pub` file into the text box and click
	the add button. Gerrit only understands SSH version 2 public keys.
	Keys may be supplied in either the OpenSSH format (key starts with
	`ssh-rsa` or `ssh-dss`) or the RFC 4716 format (file starts with
	`---- BEGIN SSH2 PUBLIC KEY ----`).

	Typically SSH keys are stored in your home directory, under `~/.ssh`.
	If you don't have any keys yet, you can create a new one and protect
	it with a passphrase:

	====
	ssh-keygen -t rsa
	====

	Then copy the content of the public key file onto your clipboard,
	and paste it into Gerrit's web interface:

	====
	cat ~/.ssh/id_rsa.pub
	====

	[TIP]
	Users who frequently upload changes will also want to consider
	starting an `ssh-agent`, and adding their private key to the list
	managed by the agent, to reduce the frequency of entering the
	key's passphrase. Consult `man ssh-agent`, or your SSH client's
	documentation, for more details on configuration of the agent
	process and how to add the private key.

	[[test_ssh]]
	Testing Connections
	~~~~~~~~~~~~~~~~~~~

	To verify your SSH key is working correctly, try using an SSH client
	to connect to Gerrit's SSHD port. By default Gerrit runs on
	port 29418, using the same hostname as the web server:

	====
	..................................................................
	$ ssh -p 29418 sshusername@hostname

	** Welcome to Gerrit Code Review **

	Hi John Doe, you have successfully connected over SSH.

	Unfortunately, interactive shells are disabled.
	To clone a hosted Git repository, use:

	git clone ssh://sshusername@hostname:29418/REPOSITORY_NAME.git

	Connection to hostname closed.
	..................................................................
	====

	In the command above, `sshusername` was configured as `Username` on
	the `Profile` tab of the `Settings` screen. If it is not set,
	propose a name and use `Select Username` to select the name.

	To determine the port number Gerrit is running on, visit the special
	information URL `http://'hostname'/ssh_info`, and copy the port
	number from the second field:

	====
	$ curl http://hostname/ssh_info
	hostname 29418
	====

	If you are developing an automated tool to perform uploads to Gerrit,
	let the user supply the hostname or the web address for Gerrit,
	and obtain the port number on the fly from the `/ssh_info` URL.
	The returned output from this URL is always `'hostname' SP 'port'`,
	or `NOT_AVAILABLE` if the SSHD server is not currently running.


	git push
	--------

	[[push_create]]
	Create Changes
	~~~~~~~~~~~~~~

	To create new changes for review, simply push to the project's
	magical `refs/for/'branch'` ref using any Git client tool:

	====
	git push ssh://sshusername@hostname:29418/projectname HEAD:refs/for/branch
	====

	E.g. `john.doe` can use git push to upload new changes for the
	`experimental` branch of project `kernel/common`, hosted at the
	`git.example.com` Gerrit server:

	====
	git push ssh://john.doe@git.example.com:29418/kernel/common HEAD:refs/for/experimental
	====

	Each new commit uploaded by the `git push` client will be
	converted into a change record on the server. The remote ref
	`refs/for/experimental` is not actually created by Gerrit, even
	though the client's status messages may say otherwise.

	Other users (e.g. project owners) who have configured Gerrit to
	notify them of new changes will be automatically sent an email
	message when the push is completed.

	To include a short tag associated with all of the changes in the
	same group, such as the local topic branch name, append it after
	the destination branch name. In this example the short topic tag
	'driver/i42' will be saved on each change this push creates or
	updates:

	====
	git push ssh://john.doe@git.example.com:29418/kernel/common HEAD:refs/for/experimental%topic=driver/i42
	====

	If you are frequently uploading changes to the same Gerrit server,
	consider adding an SSH host block in `~/.ssh/config` to remember
	your username, hostname and port number. This permits the use of
	shorter URLs on the command line, such as:

	====
	$ cat ~/.ssh/config
	...
	Host tr
	Hostname git.example.com
	Port 29418
	User john.doe

	$ git push tr:kernel/common HEAD:refs/for/experimental
	====

	Specific reviewers can be requested and/or additional 'carbon
	copies' of the notification message may be sent by including these
	as options in the reference

	====
	git push tr:kernel/common HEAD:refs/for/experimental%r=a@a.com,cc=b@o.com
	====

	The `r='email'` and `cc='email'` options may be specified as many
	times as necessary to cover all interested parties. Gerrit will
	automatically avoid sending duplicate email notifications, such as
	if one of the specified reviewers or CC addresses had also requested
	to receive all new change notifications.

	If you are frequently sending changes to the same parties and/or
	branches, consider adding a custom remote block to your project's
	`.git/config` file:

	====
	$ cat .git/config
	...
	[remote "exp"]
	url = tr:kernel/common
	push = HEAD:refs/for/experimental%r=a@a.com,cc=b@o.com

	$ git push exp
	====


	[[push_replace]]
	Replace Changes
	~~~~~~~~~~~~~~~

	To add an additional patch set to a change, ensure Change-Id
	lines were created in the original commit messages, and just use
	`git push URL HEAD:refs/for/...` as <<push_create,described above>>.
	Gerrit Code Review will automatically match the commits back to
	their original changes by taking advantage of the Change-Id lines.

	If Change-Id lines are not present in the commit messages, consider
	amending the message and copying the line from the change's page
	on the web, and then using `git push` as described above.

	If Change-Id lines are not available, then the user must use the
	manual mapping technique described below.

	For more about Change-Ids, see link:user-changeid.html[Change-Id Lines].

	[[manual_replacement_mapping]]
	Manual Replacement Mapping
	^^^^^^^^^^^^^^^^^^^^^^^^^^

	.Deprecation Warning
	****
	The remainder of this section describes a manual method of replacing
	changes by matching each commit name to an existing change number.
	End-users should instead prefer to use Change-Id lines in their
	commit messages, as the process is then fully automated by Gerrit
	during normal uploads.

	See above for the preferred technique of replacing changes.
	****

	To add an additional patch set to a change, replacing it with an
	updated version of the same logical modification, send the new
	commit to the change's ref. For example, to add the commit whose
	SHA-1 starts with `c0ffee` as a new patch set for change number
	`1979`, use the push refspec `c0ffee:refs/changes/1979` as below:

	====
	git push ssh://sshusername@hostname:29418/projectname c0ffee:refs/changes/1979
	====

	This form can be combined together with `refs/for/'branchname'`
	(above) to simultaneously create new changes and replace changes
	during one network transaction.

	For example, consider the following sequence of events:

	====
	$ git commit -m A ; # create 3 commits
	$ git commit -m B
	$ git commit -m C

	$ git push ... HEAD:refs/for/master ; # upload for review
	... A is 1500 ...
	... B is 1501 ...
	... C is 1502 ...

	$ git rebase -i HEAD~3 ; # edit "A", insert D before B
	; # now series is A'-D-B'-C'
	$ git push ...
	HEAD:refs/for/master
	HEAD~3:refs/changes/1500
	HEAD~1:refs/changes/1501
	HEAD~0:refs/changes/1502 ; # upload replacements
	====

	At the final step during the push Gerrit will attach A' as a new
	patch set on change 1500; B' as a new patch set on change 1501; C'
	as a new patch set on 1502; and D will be created as a new change.

	Ensuring D is created as a new change requires passing the refspec
	`HEAD:refs/for/branchname`, otherwise Gerrit will ignore D and
	won't do anything with it. For this reason it is a good idea to
	always include the create change refspec when uploading replacements.


	[[bypass_review]]
	Bypass Review
	~~~~~~~~~~~~~

	Changes (and annotated tags) can be pushed directly into a
	repository, bypassing the review process. This is primarily useful
	for a project owner to create new branches, create annotated tags
	for releases, or to force-update a branch whose history needed to
	be rewritten.

	Gerrit restricts direct pushes that bypass review to:

	* `refs/heads/*`: any branch can be updated, created, deleted,
	or rewritten by the pusher.
	* `refs/tags/*`: annotated tag objects pointing to any other type
	of Git object can be created.

	To push branches, the proper access rights must be configured first.
	Here follows a few examples of how to configure this in Gerrit:

	* Update: Any existing branch can be fast-forwarded to a new commit.
	This is the safest mode as commits cannot be discarded. Creation
	of new branches is rejected. Can be configured with
	link:access-control.html#category_push_direct['Push'] access.
	* Create: Allows creation of a new branch if the name does not
	already designate an existing branch name. Needs
	link:access-control.html#category_create['Create Reference']
	configured. Please note that once created, this permission doesn't
	grant the right to update the branch with further commits (see above
	for update details).
	* Delete: Implies Update, but also allows an existing
	branch to be deleted. Since a force push is effectively a delete
	followed by a create, but performed atomically on the server and
	logged, this also permits forced push updates to branches.
	To grant this access, configure
	link:access-control.html#category_push_direct['Push'] with the
	'Force' option ticked.

	To push annotated tags, the `Push Annotated Tag` project right must
	be granted to one (or more) of the user's groups. There is only
	one level of access in this category.

	Project owners may wish to grant themselves `Push Annotated Tag`
	only at times when a new release is being prepared, and otherwise
	grant nothing at all. This ensures that accidental pushes don't
	make undesired changes to the public repository.


	repo upload
	-----------

	repo is a multiple repository management tool, most commonly
	used by the Android Open Source Project. For more details, see
	link:http://source.android.com/source/using-repo.html[using repo].

	[[repo_create]]
	Create Changes
	~~~~~~~~~~~~~~

	To upload changes to a project using `repo`, ensure the manifest's
	review field has been configured to point to the Gerrit server.
	Only the hostname or the web address needs to be given in the
	manifest file. During upload `repo` will automatically determine the
	correct port number by reading `http://'reviewhostname'/ssh_info`
	when its invoked.

	Each new commit uploaded by `repo upload` will be converted into
	a change record on the server. Other users (e.g. project owners)
	who have configured Gerrit to notify them of new changes will be
	automatically sent an email message. Additional notifications can
	be sent through command line options.

	For more details on using `repo upload`, see `repo help upload`.

	[[repo_replace]]
	Replace Changes
	~~~~~~~~~~~~~~~

	To replace changes, ensure Change-Id lines were created in the
	commit messages, and just use `repo upload`.
	Gerrit Code Review will automatically match the commits back to
	their original changes by taking advantage of their Change-Id lines.

	If Change-Id lines are not present in the commit messages, consider
	amending the message and copying the line from the change's page
	on the web.

	If Change-Id lines are not available, then the user must use the much
	more <<manual_replacement_mapping,manual mapping technique>> offered
	by using `git push` to a specific `refs/changes/change#` reference.

	For more about Change-Ids, see link:user-changeid.html[Change-Id Lines].


	Gritty Details
	--------------

	As Gerrit implements the entire SSH and Git server stack within its
	own process space, Gerrit maintains complete control over how the
	repository is updated, and what responses are sent to the `git push`
	client invoked by the end-user, or by `repo upload`. This allows
	Gerrit to provide magical refs, such as `refs/for/*` for new
	change submission and `refs/changes/*` for change replacement.
	When a push request is received to create a ref in one of these
	namespaces Gerrit performs its own logic to update the database,
	and then lies to the client about the result of the operation.
	A successful result causes the client to believe that Gerrit has
	created the ref, but in reality Gerrit hasn't created the ref at all.

	By implementing the entire server stack, Gerrit is also able to
	perform project level access control checks (to verify the end-user
	is permitted to access a project) prior to advertising the available
	refs, and potentially leaking information to a snooping client.
	Clients cannot tell the difference between 'project not found' and
	'project exists, but access is denied'.

	Gerrit can also ensure users have completed a valid Contributor
	Agreement prior to accepting any transferred objects, and if an
	agreement is required, but not completed, it aborts the network
	connection before data is sent. This ensures that project owners
	can be certain any object available in their repository has been
	supplied under at least one valid agreement.

	GERRIT
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