Project

General

Profile

Gerrit » History » Version 54

neels, 10/13/2016 02:40 AM

1 1 zecke
h1. Contributing using Gerrit
2 1 zecke
3 11 laforge
{{>toc}}
4 11 laforge
5 10 laforge
At [[OpenBSC:OsmoDevCon2016]] we discussed problems with our past contribution / patch submission process using mails on the mailing list as well as patchwork.  The result is that we want to give Gerrit a try for some time and see if it helps us to have a better process
6 1 zecke
7 10 laforge
Gerrit is a review tool that integrates nicely with git and ssh. You can find general information about Gerrit at https://www.gerritcodereview.com/
8 1 zecke
9 10 laforge
The advantages of Gerrit are:
10 10 laforge
* patch submission status is automatically tracked, also with several revisions for a patch set.
11 10 laforge
* patches are build-tested (and possibly even further tested) by jenkins before they are applied
12 10 laforge
* developers + maintainers can formally vote on a patch (developer: -1/0/+1, maintainer: -2/0/+2)
13 10 laforge
* once a patch has +2 score, it can be (automatically) merged into master
14 10 laforge
* patch sumissions not via git send-email but direcly from git
15 10 laforge
16 10 laforge
h2. Osmocom Subprojects using Gerrit
17 10 laforge
18 1 zecke
The following projects use Gerrit to contribute changes:
19 1 zecke
20 1 zecke
* libosmocore.git
21 1 zecke
* libosmo-abis.git
22 1 zecke
* libosmo-netif.git
23 1 zecke
* libosmo-sccp.git
24 1 zecke
* libsmpp34.git
25 1 zecke
* openbsc.git
26 1 zecke
* osmo-bts.git
27 1 zecke
* osmo-iuh.git
28 1 zecke
* osmo-pcu.git
29 5 zecke
* cellmgr-ng.git
30 1 zecke
* osmo-sip-connector.git
31 30 neels
32 1 zecke
h2. Configuring Gerrit/Account
33 1 zecke
34 54 neels
You will need to sign-up at https://gerrit.osmocom.org/login/. If you have an Osmocom Redmine account you can use https://osmocom.org/openid as OpenID provider.
35 1 zecke
36 54 neels
* first sign in on https://osmocom.org
37 54 neels
* go to https://gerrit.osmocom.org and klick "Sign in"
38 54 neels
* enter https://osmocom.org/openid
39 54 neels
40 54 neels
If you have no Osmocom redmine account, you can simply create one online at the "Register" link in the upper right corner.
41 10 laforge
Even without an existing or new redmine account, you should also be able to use any other OpenID provider to authenticate against gerrit (untested).
42 10 laforge
43 10 laforge
After the initial sign-up you will need to:
44 1 zecke
45 1 zecke
* Pick a username (can not be changed)
46 1 zecke
* Add your public ssh key(s)
47 1 zecke
* Add email addresses you intend to use as author/comitter
48 30 neels
49 30 neels
If you would like to push private branches to the Gerrit repository, you also need to be added to the "known users" group.
50 30 neels
Please send a short requesting email to openbsc@lists.osmocom.org.
51 1 zecke
52 1 zecke
h2. Setting up Gerrit for commits and pushing
53 1 zecke
54 33 neels
*Note:* it is easiest to work with gerrit when gerrit is the only remote in your git clone.
55 33 neels
When you clone from git.osmocom.org and add the gerrit remote, git will have two remotes,
56 36 neels
so when you first checkout a branch you have to supply the remote explicitly (cumbersome).
57 34 neels
The gerrit repositories and git.osmocom.org are constantly synced, so it is sufficient
58 34 neels
to clone from gerrit only.
59 33 neels
60 33 neels
h3. Simplest: new clone
61 33 neels
62 35 neels
* Create a new clone from gerrit
63 35 neels
* Fetch the commit hook that adds Change-Id to each commit to uniquely identify a commit
64 42 neels
65 33 neels
<pre>
66 33 neels
git clone ssh://$USERNAME@gerrit.osmocom.org:29418/$PROJECT.git
67 33 neels
scp -P 29418 $USERNAME@gerrit.osmocom.org:hooks/commit-msg $PROJECT/.git/hooks/
68 33 neels
</pre>
69 33 neels
70 33 neels
h3. SSH config
71 33 neels
72 33 neels
In '~/.ssh/config', add these lines:
73 33 neels
<pre>
74 52 neels
Host go
75 33 neels
Hostname gerrit.osmocom.org
76 33 neels
Port 29418
77 33 neels
User $USERNAME
78 33 neels
</pre>
79 52 neels
('go' means gerrit.osmocom, replace with your favorite shortcut name,
80 33 neels
replace '$USERNAME' with your user name as used on the gerrit website)
81 33 neels
82 33 neels
Then you can shorten above commands to
83 1 zecke
<pre>
84 52 neels
git clone ssh://go/$PROJECT.git
85 51 neels
cd $PROJECT
86 51 neels
scp go:hooks/commit-msg .git/hooks/
87 33 neels
</pre>
88 33 neels
89 46 neels
h3. Committer must match
90 46 neels
91 47 neels
Your email address on gerrit and the email address git places in your
92 46 neels
commits must match, or you will get rejected with an error message like
93 46 neels
"invalid commiter". You can add email addresses on the gerrit web UI.
94 46 neels
95 33 neels
h3. Add gerrit to an existing clone
96 33 neels
97 7 neels
* Add the remote to be able to fetch and push to gerrit
98 7 neels
* Fetch the commit hook that adds Change-Id to each commit to uniquely identify a commit
99 7 neels
100 7 neels
<pre>
101 7 neels
USERNAME=gerrit_user_name
102 7 neels
PROJECT=$(basename $PWD)
103 1 zecke
git remote add gerrit ssh://$USERNAME@gerrit.osmocom.org:29418/$PROJECT.git
104 1 zecke
scp -P 29418 $USERNAME@gerrit.osmocom.org:hooks/commit-msg .git/hooks/
105 44 neels
</pre>
106 44 neels
107 33 neels
h2. Push for review
108 1 zecke
109 38 neels
Checkout the revision or branch that you want to submit for review, then
110 38 neels
111 31 neels
<pre>
112 48 ahuemer
git push gerrit HEAD:refs/for/master
113 1 zecke
</pre>
114 38 neels
115 1 zecke
You can optionally add a topic name with
116 40 neels
117 40 neels
<pre>
118 48 ahuemer
git push gerrit HEAD:refs/for/master/my_topic
119 38 neels
</pre>
120 38 neels
121 1 zecke
122 38 neels
h2. Push a "private" user branch
123 33 neels
124 1 zecke
*Note* that you must be a member of the "known users" group, see above.
125 33 neels
126 43 neels
If your local branch name is of the form 'your_name/topic', you can just
127 1 zecke
<pre>
128 1 zecke
git push
129 33 neels
</pre>
130 41 neels
and git will tell you what to do.
131 1 zecke
132 41 neels
To push from a "nonstandard" local branch name, do
133 41 neels
<pre>
134 50 msuraev
git push gerrit HEAD:refs/heads/user/$USERNAME/branch_name
135 33 neels
</pre>
136 33 neels
137 39 neels
138 39 neels
h2. List changesets in gerrit
139 39 neels
140 7 neels
<pre>
141 48 ahuemer
git ls-remote gerrit changes/*
142 2 zecke
</pre>
143 12 msuraev
144 17 neels
h1. Tips and Tricks
145 1 zecke
146 17 neels
h2. Throw-away branch
147 17 neels
148 17 neels
If you need to adjust and re-submit patches, it may be handy to create a throw-away branch ("R D" in magit-gerrit in emacs for example),
149 45 neels
make your changes/amendments and then send patch(es) back to gerrit while removing temporary branch automatically with "git review -f".
150 13 neels
151 25 neels
h2. Re-submit a Branch with Amended Commits
152 13 neels
153 1 zecke
On a feature branch, one typically has numerous commits that depend on their preceding commits.
154 29 neels
Often, some of the branch commits need to be amended for fixes. But, Gerrit will refuse your branch
155 29 neels
re-submission if the first branch commit is unchanged.
156 1 zecke
157 16 neels
To re-submit a branch, make sure to cosmetically tweak the branch's first commit log message
158 22 neels
before each re-submission (keep the Change-Id, really make just a cosmetic change).
159 13 neels
160 16 neels
<pre>
161 16 neels
git rebase -i master
162 16 neels
# replace the first line's 'pick' with 'r' (or 'reword'), exit editor
163 16 neels
# git presents you with commit log message, make any tiny modification.
164 1 zecke
</pre>
165 1 zecke
166 29 neels
The cause: Gerrit refuses to accept a commit with a Change-Id that it already knows and
167 29 neels
where the commit hash is identical.
168 1 zecke
169 29 neels
If you just cosmetically tweak the first commit's log message, the commit hash
170 29 neels
is changed. Since the following commits contain their predecessor's commit hash, now
171 29 neels
all of the branch's commit hashes are modified, and gerrit happily accepts them as a 
172 29 neels
new patch set. It will still pick up the Change-Ids (which you shouldn't edit) and 
173 29 neels
notice if commits have remained identical (keeping the votes). But with the minor
174 29 neels
commit log tweak, it will no longer thwart your re-submission with an error message.
175 29 neels
176 29 neels
Note: you could modify all the Change-Ids, but now your branch submission would
177 29 neels
open entirely new review entries and you would have to abandon your previous submission.
178 29 neels
Comments on the first submission are lost and you cannot diff between patch sets.
179 29 neels
180 29 neels
181 26 neels
h2. Re-submit Previously Abandoned Changes
182 16 neels
183 16 neels
You have to edit the Change-Ids, on a branch that would be every single commit log message.
184 16 neels
185 13 neels
<pre>
186 1 zecke
cd openbsc
187 1 zecke
git co my-branch
188 1 zecke
git rebase -i master
189 1 zecke
# replace all 'pick' with 'r' (or 'reword'), exit your editor
190 13 neels
# git presents each commit log message for editing
191 13 neels
</pre>
192 13 neels
193 27 neels
h2. Submit a "private" branch for master
194 21 neels
195 21 neels
If you've pushed a branch to refs/heads/* somewhere, gerrit will already know the Change-Ids on it.
196 24 neels
Make sure the option [[Gerrit#Private-Branches-Create-a-new-change-for-every-commit|Create a new change for every commit not in the target branch]] is _TRUE_ for your project,
197 21 neels
or gerrit will refuse to accept your submission.
198 21 neels
199 16 neels
h1. Reasons for Particular Configuration
200 13 neels
201 16 neels
h2. Rebase if necessary
202 16 neels
203 16 neels
There are different merge strategies that Gerrit performs to accept patches.
204 13 neels
Each project can be configured to a specific merge strategy, but unfortunately you can't
205 13 neels
decide on a strategy per patch submission.
206 13 neels
207 13 neels
It seems that the "Merge if Necessary" strategy is best supported, but it creates non-linear
208 13 neels
history with numerous merge commits that are usually not at all necessary.
209 13 neels
210 13 neels
Instead, the "Cherry Pick" strategy puts each patch onto current master's HEAD to create
211 13 neels
linear history. However, this will cause merge failures as soon as one patch depends on
212 13 neels
another submitted patch, as typical for a feature branch submission.
213 13 neels
214 1 zecke
So we prefer the "Rebase if Necessary" strategy, which always tries to apply your patches to
215 13 neels
the current master HEAD, in sequence with the previous patches on the same branch.
216 13 neels
However, some problems still remain, including some bugs in "Rebase if Necessary".
217 1 zecke
218 13 neels
There's a problem with "Rebase if Necessary": If your branch sits at master's HEAD, Gerrit
219 13 neels
refuses to accept the submission, because it thinks that no new changes are submitted.
220 13 neels
This is a bug in Gerrit, which holger has fixed manually in our Gerrit installation:
221 1 zecke
222 1 zecke
https://bugs.chromium.org/p/gerrit/issues/detail?id=4158
223 1 zecke
224 1 zecke
225 16 neels
h2. Private Branches: Create a new change for every commit...
226 1 zecke
227 13 neels
Say you have an extensive feature in development, and you want to keep it on the
228 13 neels
upstream git repository to a) keep it safe and b) collaborate with other devs on it.
229 16 neels
So, of course, you have regularly pushed to refs/heads/yoyodyne/feature.
230 13 neels
231 13 neels
Since you have the gerrit commit hook installed, your feature branch already has
232 13 neels
Change-Id tags in all commit log messages.
233 13 neels
234 13 neels
Now your feature is complete and you would like to submit it to master.
235 13 neels
Alas, Gerrit refuses to accept your patch submission for master, because it
236 13 neels
knows the Change-Ids are also on a different branch.
237 13 neels
238 16 neels
Gerrit by default enforces that a Change-Id must be unique across all branches,
239 16 neels
so that each submission for review is separate for each branch. Instead, we
240 16 neels
want to handle Change-Ids per-branch, so that you can have the same change
241 16 neels
submitted to different branches, as separate patch submissions, without having
242 16 neels
to cosmetically adjust the Change-Id.
243 13 neels
244 16 neels
Solution: set the option 
245 16 neels
_Create a new change for every commit not in the target branch_ to _TRUE_
246 13 neels
247 20 neels
h2. Allow content merges
248 14 neels
249 14 neels
By default, gerrit compares patches only by the files' paths. If two paths are the same,
250 14 neels
it immediately shows them as conflicts (path conflicts).
251 14 neels
252 14 neels
In software development, a conflict usually means an actual content conflict, so if the
253 14 neels
edits are in two entirely separate places in the file, we don't consider this a conflict.
254 14 neels
255 23 neels
By setting _Allow content merges_ to _TRUE_ in the git project config, we tell Gerrit to
256 14 neels
perform text merges of the submitted patches and only complain about actual content
257 14 neels
conflicts, in the usual software engineering sense.
258 32 neels
259 32 neels
h1. Admin
260 32 neels
261 32 neels
h2. Adding users to groups
262 32 neels
263 32 neels
Normally, the gerrit UI auto-completes a user name in the edit field. It has happened
264 32 neels
though that an existing user is not auto-completed, as if it didn't exist. In that case,
265 32 neels
find out the user ID (seven digit number like 1000123) and just enter that.
266 32 neels
267 32 neels
The user ID can be found on the user's "Settings" page, or in the database (s.b.).
268 32 neels
269 32 neels
h2. Querying the database directly
270 32 neels
271 32 neels
If your user has permission to access the database, you can place SQL queries using the
272 32 neels
'gerrit gsql' commands over ssh:
273 32 neels
274 32 neels
<pre>
275 53 neels
ssh go 'gerrit gsql --format PRETTY -c "show tables"'
276 53 neels
ssh go 'gerrit gsql --format PRETTY -c "select full_name,account_id from accounts"'
277 1 zecke
</pre>
278 53 neels
279 53 neels
(see ~/.ssh/config above for the 'go' shortcut)
280 32 neels
281 32 neels
This seems to be the MySQL dialect.
Add picture from clipboard (Maximum size: 48.8 MB)