Project

General

Profile

Gerrit » History » Version 41

neels, 07/12/2016 01:11 PM

1 1 zecke
h1. Contributing using Gerrit
2
3 11 laforge
{{>toc}}
4
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
* patch submission status is automatically tracked, also with several revisions for a patch set.
11
* patches are build-tested (and possibly even further tested) by jenkins before they are applied
12
* developers + maintainers can formally vote on a patch (developer: -1/0/+1, maintainer: -2/0/+2)
13
* once a patch has +2 score, it can be (automatically) merged into master
14
* patch sumissions not via git send-email but direcly from git
15
16
h2. Osmocom Subprojects using Gerrit
17
18 1 zecke
The following projects use Gerrit to contribute changes:
19
20
* libosmocore.git
21
* libosmo-abis.git
22
* libosmo-netif.git
23
* libosmo-sccp.git
24
* libsmpp34.git
25
* openbsc.git
26
* osmo-bts.git
27
* osmo-iuh.git
28
* 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
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
36
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
38
After the initial sign-up you will need to:
39 1 zecke
40
* Pick a username (can not be changed)
41
* Add your public ssh key(s)
42
* Add email addresses you intend to use as author/comitter
43 30 neels
44
If you would like to push private branches to the Gerrit repository, you also need to be added to the "known users" group.
45
Please send a short requesting email to openbsc@lists.osmocom.org.
46 1 zecke
47
h2. Setting up Gerrit for commits and pushing
48
49 33 neels
*Note:* it is easiest to work with gerrit when gerrit is the only remote in your git clone.
50
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
to clone from gerrit only.
54 33 neels
55
h3. Simplest: new clone
56
57 35 neels
* Create a new clone from gerrit
58
* Fetch the commit hook that adds Change-Id to each commit to uniquely identify a commit
59 33 neels
<pre>
60
git clone ssh://$USERNAME@gerrit.osmocom.org:29418/$PROJECT.git
61
scp -P 29418 $USERNAME@gerrit.osmocom.org:hooks/commit-msg $PROJECT/.git/hooks/
62
</pre>
63
64
h3. SSH config
65
66
In '~/.ssh/config', add these lines:
67
<pre>
68
Host foo
69
Hostname gerrit.osmocom.org
70
Port 29418
71
User $USERNAME
72
</pre>
73
(replace 'foo' with your favorite shortcut name,
74
replace '$USERNAME' with your user name as used on the gerrit website)
75
76
Then you can shorten above commands to
77 1 zecke
<pre>
78 33 neels
git clone ssh://foo/$PROJECT.git
79 35 neels
scp foo:hooks/commit-msg $PROJECT/.git/hooks/
80 33 neels
</pre>
81
82
h3. Add gerrit to an existing clone
83
84 7 neels
* Add the remote to be able to fetch and push to gerrit
85
* Fetch the commit hook that adds Change-Id to each commit to uniquely identify a commit
86
87
<pre>
88
USERNAME=gerrit_user_name
89
PROJECT=$(basename $PWD)
90
git remote add gerrit ssh://$USERNAME@gerrit.osmocom.org:29418/$PROJECT.git
91
scp -P 29418 $USERNAME@gerrit.osmocom.org:hooks/commit-msg .git/hooks/
92
</pre>
93
94 33 neels
h2. Push for review
95 1 zecke
96 38 neels
Checkout the revision or branch that you want to submit for review, then
97
98 31 neels
<pre>
99 40 neels
git push origin HEAD:refs/for/master
100 1 zecke
</pre>
101 38 neels
102 1 zecke
You can optionally add a topic name with
103 40 neels
104
<pre>
105
git push origin HEAD:refs/for/master/my_topic
106
</pre>
107
108
If you've added gerrit as a remote named 'gerrit', instead use:
109 38 neels
110
<pre>
111
git push gerrit HEAD:refs/for/master/my_topic
112
</pre>
113
114 33 neels
h2. Push a "private" user branch
115
116
*Note* that you must be a member of the "known users" group, see above.
117 1 zecke
118 33 neels
If gerrit is your only remote, and if your local branch name is of the
119 41 neels
form 'your_name/topic', you can just
120 1 zecke
<pre>
121
git push
122 33 neels
</pre>
123 41 neels
and git will tell you what to do.
124 1 zecke
125 41 neels
To push from a "nonstandard" local branch name, do
126 33 neels
<pre>
127 41 neels
git push origin HEAD:refs/heads/$USERNAME/branch_name
128 31 neels
</pre>
129 7 neels
130 41 neels
If you've added gerrit as a secondary remote named 'gerrit', instead do
131 33 neels
<pre>
132 41 neels
git push gerrit
133 33 neels
</pre>
134 41 neels
135 33 neels
136
h2. List changesets in gerrit
137 39 neels
138
If gerrit is your only remote:
139
140
<pre>
141
git ls-remote origin changes/*
142
</pre>
143
144
or, if you've added gerrit as a second remote:
145
146 7 neels
<pre>
147
git ls-remote gerrit changes/*
148 2 zecke
</pre>
149 12 msuraev
150 17 neels
h1. Tips and Tricks
151 1 zecke
152 17 neels
h2. Throw-away branch
153
154
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),
155
make your changes/amendments and than send patch(es) back to gerrit while removing temporary branch automatically with "git review -f".
156 13 neels
157 25 neels
h2. Re-submit a Branch with Amended Commits
158 13 neels
159 1 zecke
On a feature branch, one typically has numerous commits that depend on their preceding commits.
160 29 neels
Often, some of the branch commits need to be amended for fixes. But, Gerrit will refuse your branch
161
re-submission if the first branch commit is unchanged.
162 1 zecke
163 16 neels
To re-submit a branch, make sure to cosmetically tweak the branch's first commit log message
164 22 neels
before each re-submission (keep the Change-Id, really make just a cosmetic change).
165 13 neels
166 16 neels
<pre>
167
git rebase -i master
168
# replace the first line's 'pick' with 'r' (or 'reword'), exit editor
169
# git presents you with commit log message, make any tiny modification.
170 1 zecke
</pre>
171
172 29 neels
The cause: Gerrit refuses to accept a commit with a Change-Id that it already knows and
173
where the commit hash is identical.
174 1 zecke
175 29 neels
If you just cosmetically tweak the first commit's log message, the commit hash
176
is changed. Since the following commits contain their predecessor's commit hash, now
177
all of the branch's commit hashes are modified, and gerrit happily accepts them as a 
178
new patch set. It will still pick up the Change-Ids (which you shouldn't edit) and 
179
notice if commits have remained identical (keeping the votes). But with the minor
180
commit log tweak, it will no longer thwart your re-submission with an error message.
181
182
Note: you could modify all the Change-Ids, but now your branch submission would
183
open entirely new review entries and you would have to abandon your previous submission.
184
Comments on the first submission are lost and you cannot diff between patch sets.
185
186
187 26 neels
h2. Re-submit Previously Abandoned Changes
188 16 neels
189
You have to edit the Change-Ids, on a branch that would be every single commit log message.
190
191 13 neels
<pre>
192 1 zecke
cd openbsc
193
git co my-branch
194
git rebase -i master
195
# replace all 'pick' with 'r' (or 'reword'), exit your editor
196 13 neels
# git presents each commit log message for editing
197
</pre>
198
199 27 neels
h2. Submit a "private" branch for master
200 21 neels
201
If you've pushed a branch to refs/heads/* somewhere, gerrit will already know the Change-Ids on it.
202 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,
203 21 neels
or gerrit will refuse to accept your submission.
204
205 16 neels
h1. Reasons for Particular Configuration
206 13 neels
207 16 neels
h2. Rebase if necessary
208
209
There are different merge strategies that Gerrit performs to accept patches.
210 13 neels
Each project can be configured to a specific merge strategy, but unfortunately you can't
211
decide on a strategy per patch submission.
212
213
It seems that the "Merge if Necessary" strategy is best supported, but it creates non-linear
214
history with numerous merge commits that are usually not at all necessary.
215
216
Instead, the "Cherry Pick" strategy puts each patch onto current master's HEAD to create
217
linear history. However, this will cause merge failures as soon as one patch depends on
218
another submitted patch, as typical for a feature branch submission.
219
220 1 zecke
So we prefer the "Rebase if Necessary" strategy, which always tries to apply your patches to
221 13 neels
the current master HEAD, in sequence with the previous patches on the same branch.
222
However, some problems still remain, including some bugs in "Rebase if Necessary".
223 1 zecke
224 13 neels
There's a problem with "Rebase if Necessary": If your branch sits at master's HEAD, Gerrit
225
refuses to accept the submission, because it thinks that no new changes are submitted.
226
This is a bug in Gerrit, which holger has fixed manually in our Gerrit installation:
227 1 zecke
228
https://bugs.chromium.org/p/gerrit/issues/detail?id=4158
229
230
231 16 neels
h2. Private Branches: Create a new change for every commit...
232 1 zecke
233 13 neels
Say you have an extensive feature in development, and you want to keep it on the
234
upstream git repository to a) keep it safe and b) collaborate with other devs on it.
235 16 neels
So, of course, you have regularly pushed to refs/heads/yoyodyne/feature.
236 13 neels
237
Since you have the gerrit commit hook installed, your feature branch already has
238
Change-Id tags in all commit log messages.
239
240
Now your feature is complete and you would like to submit it to master.
241
Alas, Gerrit refuses to accept your patch submission for master, because it
242
knows the Change-Ids are also on a different branch.
243
244 16 neels
Gerrit by default enforces that a Change-Id must be unique across all branches,
245
so that each submission for review is separate for each branch. Instead, we
246
want to handle Change-Ids per-branch, so that you can have the same change
247
submitted to different branches, as separate patch submissions, without having
248
to cosmetically adjust the Change-Id.
249 13 neels
250 16 neels
Solution: set the option 
251
_Create a new change for every commit not in the target branch_ to _TRUE_
252 13 neels
253 20 neels
h2. Allow content merges
254 14 neels
255
By default, gerrit compares patches only by the files' paths. If two paths are the same,
256
it immediately shows them as conflicts (path conflicts).
257
258
In software development, a conflict usually means an actual content conflict, so if the
259
edits are in two entirely separate places in the file, we don't consider this a conflict.
260
261 23 neels
By setting _Allow content merges_ to _TRUE_ in the git project config, we tell Gerrit to
262 14 neels
perform text merges of the submitted patches and only complain about actual content
263
conflicts, in the usual software engineering sense.
264 32 neels
265
h1. Admin
266
267
h2. Adding users to groups
268
269
Normally, the gerrit UI auto-completes a user name in the edit field. It has happened
270
though that an existing user is not auto-completed, as if it didn't exist. In that case,
271
find out the user ID (seven digit number like 1000123) and just enter that.
272
273
The user ID can be found on the user's "Settings" page, or in the database (s.b.).
274
275
h2. Querying the database directly
276
277
If your user has permission to access the database, you can place SQL queries using the
278
'gerrit gsql' commands over ssh:
279
280
<pre>
281
ssh -p 29418 $USERNAME@gerrit.osmocom.org 'gerrit gsql --format PRETTY -c "show tables"'
282
ssh -p 29418 $USERNAME@gerrit.osmocom.org 'gerrit gsql --format PRETTY -c "select full_name,account_id from accounts"'
283
</pre>
284
285
This seems to be the MySQL dialect.
Add picture from clipboard (Maximum size: 48.8 MB)