Project

General

Profile

Gerrit » History » Version 49

ahuemer, 09/06/2016 10:12 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 42 neels
60 33 neels
<pre>
61
git clone ssh://$USERNAME@gerrit.osmocom.org:29418/$PROJECT.git
62
scp -P 29418 $USERNAME@gerrit.osmocom.org:hooks/commit-msg $PROJECT/.git/hooks/
63
</pre>
64
65
h3. SSH config
66
67
In '~/.ssh/config', add these lines:
68
<pre>
69
Host foo
70
Hostname gerrit.osmocom.org
71
Port 29418
72
User $USERNAME
73
</pre>
74
(replace 'foo' with your favorite shortcut name,
75
replace '$USERNAME' with your user name as used on the gerrit website)
76
77
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 $PROJECT/.git/hooks/
81 33 neels
</pre>
82
83 46 neels
h3. Committer must match
84
85 47 neels
Your email address on gerrit and the email address git places in your
86 46 neels
commits must match, or you will get rejected with an error message like
87
"invalid commiter". You can add email addresses on the gerrit web UI.
88
89 33 neels
h3. Add gerrit to an existing clone
90
91 7 neels
* Add the remote to be able to fetch and push to gerrit
92
* Fetch the commit hook that adds Change-Id to each commit to uniquely identify a commit
93
94
<pre>
95
USERNAME=gerrit_user_name
96
PROJECT=$(basename $PWD)
97 1 zecke
git remote add gerrit ssh://$USERNAME@gerrit.osmocom.org:29418/$PROJECT.git
98
scp -P 29418 $USERNAME@gerrit.osmocom.org:hooks/commit-msg .git/hooks/
99 44 neels
</pre>
100
101 33 neels
h2. Push for review
102 1 zecke
103 38 neels
Checkout the revision or branch that you want to submit for review, then
104
105 31 neels
<pre>
106 48 ahuemer
git push gerrit HEAD:refs/for/master
107 1 zecke
</pre>
108 38 neels
109 1 zecke
You can optionally add a topic name with
110 40 neels
111
<pre>
112 48 ahuemer
git push gerrit HEAD:refs/for/master/my_topic
113 38 neels
</pre>
114
115 1 zecke
116 38 neels
h2. Push a "private" user branch
117 33 neels
118 1 zecke
*Note* that you must be a member of the "known users" group, see above.
119 33 neels
120 43 neels
If your local branch name is of the form 'your_name/topic', you can just
121 1 zecke
<pre>
122
git push
123 33 neels
</pre>
124 41 neels
and git will tell you what to do.
125 1 zecke
126 41 neels
To push from a "nonstandard" local branch name, do
127
<pre>
128 48 ahuemer
git push gerrit HEAD:refs/heads/$USERNAME/branch_name
129 33 neels
</pre>
130
131 39 neels
132
h2. List changesets in gerrit
133
134 7 neels
<pre>
135 48 ahuemer
git ls-remote gerrit changes/*
136 2 zecke
</pre>
137 12 msuraev
138 17 neels
h1. Tips and Tricks
139 1 zecke
140 17 neels
h2. Throw-away branch
141
142
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),
143 45 neels
make your changes/amendments and then send patch(es) back to gerrit while removing temporary branch automatically with "git review -f".
144 13 neels
145 25 neels
h2. Re-submit a Branch with Amended Commits
146 13 neels
147 1 zecke
On a feature branch, one typically has numerous commits that depend on their preceding commits.
148 29 neels
Often, some of the branch commits need to be amended for fixes. But, Gerrit will refuse your branch
149
re-submission if the first branch commit is unchanged.
150 1 zecke
151 16 neels
To re-submit a branch, make sure to cosmetically tweak the branch's first commit log message
152 22 neels
before each re-submission (keep the Change-Id, really make just a cosmetic change).
153 13 neels
154 16 neels
<pre>
155
git rebase -i master
156
# replace the first line's 'pick' with 'r' (or 'reword'), exit editor
157
# git presents you with commit log message, make any tiny modification.
158 1 zecke
</pre>
159
160 29 neels
The cause: Gerrit refuses to accept a commit with a Change-Id that it already knows and
161
where the commit hash is identical.
162 1 zecke
163 29 neels
If you just cosmetically tweak the first commit's log message, the commit hash
164
is changed. Since the following commits contain their predecessor's commit hash, now
165
all of the branch's commit hashes are modified, and gerrit happily accepts them as a 
166
new patch set. It will still pick up the Change-Ids (which you shouldn't edit) and 
167
notice if commits have remained identical (keeping the votes). But with the minor
168
commit log tweak, it will no longer thwart your re-submission with an error message.
169
170
Note: you could modify all the Change-Ids, but now your branch submission would
171
open entirely new review entries and you would have to abandon your previous submission.
172
Comments on the first submission are lost and you cannot diff between patch sets.
173
174
175 26 neels
h2. Re-submit Previously Abandoned Changes
176 16 neels
177
You have to edit the Change-Ids, on a branch that would be every single commit log message.
178
179 13 neels
<pre>
180 1 zecke
cd openbsc
181
git co my-branch
182
git rebase -i master
183
# replace all 'pick' with 'r' (or 'reword'), exit your editor
184 13 neels
# git presents each commit log message for editing
185
</pre>
186
187 27 neels
h2. Submit a "private" branch for master
188 21 neels
189
If you've pushed a branch to refs/heads/* somewhere, gerrit will already know the Change-Ids on it.
190 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,
191 21 neels
or gerrit will refuse to accept your submission.
192
193 16 neels
h1. Reasons for Particular Configuration
194 13 neels
195 16 neels
h2. Rebase if necessary
196
197
There are different merge strategies that Gerrit performs to accept patches.
198 13 neels
Each project can be configured to a specific merge strategy, but unfortunately you can't
199
decide on a strategy per patch submission.
200
201
It seems that the "Merge if Necessary" strategy is best supported, but it creates non-linear
202
history with numerous merge commits that are usually not at all necessary.
203
204
Instead, the "Cherry Pick" strategy puts each patch onto current master's HEAD to create
205
linear history. However, this will cause merge failures as soon as one patch depends on
206
another submitted patch, as typical for a feature branch submission.
207
208 1 zecke
So we prefer the "Rebase if Necessary" strategy, which always tries to apply your patches to
209 13 neels
the current master HEAD, in sequence with the previous patches on the same branch.
210
However, some problems still remain, including some bugs in "Rebase if Necessary".
211 1 zecke
212 13 neels
There's a problem with "Rebase if Necessary": If your branch sits at master's HEAD, Gerrit
213
refuses to accept the submission, because it thinks that no new changes are submitted.
214
This is a bug in Gerrit, which holger has fixed manually in our Gerrit installation:
215 1 zecke
216
https://bugs.chromium.org/p/gerrit/issues/detail?id=4158
217
218
219 16 neels
h2. Private Branches: Create a new change for every commit...
220 1 zecke
221 13 neels
Say you have an extensive feature in development, and you want to keep it on the
222
upstream git repository to a) keep it safe and b) collaborate with other devs on it.
223 16 neels
So, of course, you have regularly pushed to refs/heads/yoyodyne/feature.
224 13 neels
225
Since you have the gerrit commit hook installed, your feature branch already has
226
Change-Id tags in all commit log messages.
227
228
Now your feature is complete and you would like to submit it to master.
229
Alas, Gerrit refuses to accept your patch submission for master, because it
230
knows the Change-Ids are also on a different branch.
231
232 16 neels
Gerrit by default enforces that a Change-Id must be unique across all branches,
233
so that each submission for review is separate for each branch. Instead, we
234
want to handle Change-Ids per-branch, so that you can have the same change
235
submitted to different branches, as separate patch submissions, without having
236
to cosmetically adjust the Change-Id.
237 13 neels
238 16 neels
Solution: set the option 
239
_Create a new change for every commit not in the target branch_ to _TRUE_
240 13 neels
241 20 neels
h2. Allow content merges
242 14 neels
243
By default, gerrit compares patches only by the files' paths. If two paths are the same,
244
it immediately shows them as conflicts (path conflicts).
245
246
In software development, a conflict usually means an actual content conflict, so if the
247
edits are in two entirely separate places in the file, we don't consider this a conflict.
248
249 23 neels
By setting _Allow content merges_ to _TRUE_ in the git project config, we tell Gerrit to
250 14 neels
perform text merges of the submitted patches and only complain about actual content
251
conflicts, in the usual software engineering sense.
252 32 neels
253
h1. Admin
254
255
h2. Adding users to groups
256
257
Normally, the gerrit UI auto-completes a user name in the edit field. It has happened
258
though that an existing user is not auto-completed, as if it didn't exist. In that case,
259
find out the user ID (seven digit number like 1000123) and just enter that.
260
261
The user ID can be found on the user's "Settings" page, or in the database (s.b.).
262
263
h2. Querying the database directly
264
265
If your user has permission to access the database, you can place SQL queries using the
266
'gerrit gsql' commands over ssh:
267
268
<pre>
269
ssh -p 29418 $USERNAME@gerrit.osmocom.org 'gerrit gsql --format PRETTY -c "show tables"'
270
ssh -p 29418 $USERNAME@gerrit.osmocom.org 'gerrit gsql --format PRETTY -c "select full_name,account_id from accounts"'
271
</pre>
272
273
This seems to be the MySQL dialect.
Add picture from clipboard (Maximum size: 48.8 MB)