Project

General

Profile

Gerrit » History » Version 46

neels, 07/12/2016 01:21 PM

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