Gerrit » History » Version 30
neels, 07/05/2016 10:48 AM
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 | 2 | zecke | * Add the remote to be able to fetch and push to gerrit |
50 | * Fetch the commit hook that adds Change-Id to each commit to uniquely identify a commit |
||
51 | |||
52 | <pre> |
||
53 | 7 | neels | USERNAME=gerrit_user_name |
54 | PROJECT=$(basename $PWD) |
||
55 | git remote add gerrit ssh://$USERNAME@gerrit.osmocom.org:29418/$PROJECT.git |
||
56 | scp -P 29418 $USERNAME@gerrit.osmocom.org:hooks/commit-msg .git/hooks/ |
||
57 | </pre> |
||
58 | |||
59 | * In case your local username matches the gerrit username, the setup shortens to |
||
60 | |||
61 | <pre> |
||
62 | PROJECT=$(basename $PWD) |
||
63 | git remote add gerrit ssh://gerrit.osmocom.org:29418/$PROJECT.git |
||
64 | scp -P 29418 gerrit.osmocom.org:hooks/commit-msg .git/hooks/ |
||
65 | </pre> |
||
66 | |||
67 | Then |
||
68 | |||
69 | * Push for review |
||
70 | <pre> |
||
71 | git push gerrit HEAD:refs/for/master |
||
72 | </pre> |
||
73 | |||
74 | * Push a user branch |
||
75 | <pre> |
||
76 | 9 | neels | git push gerrit HEAD:refs/heads/users/$USERNAME/topic |
77 | 7 | neels | </pre> |
78 | |||
79 | * Directly push to master if you are allowed to |
||
80 | <pre> |
||
81 | git push gerrit HEAD:refs/heads/master |
||
82 | </pre> |
||
83 | |||
84 | * List changesets in gerrit |
||
85 | <pre> |
||
86 | git ls-remote gerrit changes/* |
||
87 | 2 | zecke | </pre> |
88 | 12 | msuraev | |
89 | 17 | neels | h1. Tips and Tricks |
90 | 1 | zecke | |
91 | 17 | neels | h2. Throw-away branch |
92 | |||
93 | 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), |
||
94 | make your changes/amendments and than send patch(es) back to gerrit while removing temporary branch automatically with "git review -f". |
||
95 | 13 | neels | |
96 | 25 | neels | h2. Re-submit a Branch with Amended Commits |
97 | 13 | neels | |
98 | 1 | zecke | On a feature branch, one typically has numerous commits that depend on their preceding commits. |
99 | 29 | neels | Often, some of the branch commits need to be amended for fixes. But, Gerrit will refuse your branch |
100 | re-submission if the first branch commit is unchanged. |
||
101 | 1 | zecke | |
102 | 16 | neels | To re-submit a branch, make sure to cosmetically tweak the branch's first commit log message |
103 | 22 | neels | before each re-submission (keep the Change-Id, really make just a cosmetic change). |
104 | 13 | neels | |
105 | 16 | neels | <pre> |
106 | git rebase -i master |
||
107 | # replace the first line's 'pick' with 'r' (or 'reword'), exit editor |
||
108 | # git presents you with commit log message, make any tiny modification. |
||
109 | 1 | zecke | </pre> |
110 | |||
111 | 29 | neels | The cause: Gerrit refuses to accept a commit with a Change-Id that it already knows and |
112 | where the commit hash is identical. |
||
113 | 1 | zecke | |
114 | 29 | neels | If you just cosmetically tweak the first commit's log message, the commit hash |
115 | is changed. Since the following commits contain their predecessor's commit hash, now |
||
116 | all of the branch's commit hashes are modified, and gerrit happily accepts them as a |
||
117 | new patch set. It will still pick up the Change-Ids (which you shouldn't edit) and |
||
118 | notice if commits have remained identical (keeping the votes). But with the minor |
||
119 | commit log tweak, it will no longer thwart your re-submission with an error message. |
||
120 | |||
121 | Note: you could modify all the Change-Ids, but now your branch submission would |
||
122 | open entirely new review entries and you would have to abandon your previous submission. |
||
123 | Comments on the first submission are lost and you cannot diff between patch sets. |
||
124 | |||
125 | |||
126 | 26 | neels | h2. Re-submit Previously Abandoned Changes |
127 | 16 | neels | |
128 | You have to edit the Change-Ids, on a branch that would be every single commit log message. |
||
129 | |||
130 | 13 | neels | <pre> |
131 | 1 | zecke | cd openbsc |
132 | git co my-branch |
||
133 | git rebase -i master |
||
134 | # replace all 'pick' with 'r' (or 'reword'), exit your editor |
||
135 | 13 | neels | # git presents each commit log message for editing |
136 | </pre> |
||
137 | |||
138 | 27 | neels | h2. Submit a "private" branch for master |
139 | 21 | neels | |
140 | If you've pushed a branch to refs/heads/* somewhere, gerrit will already know the Change-Ids on it. |
||
141 | 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, |
142 | 21 | neels | or gerrit will refuse to accept your submission. |
143 | |||
144 | 16 | neels | h1. Reasons for Particular Configuration |
145 | 13 | neels | |
146 | 16 | neels | h2. Rebase if necessary |
147 | |||
148 | There are different merge strategies that Gerrit performs to accept patches. |
||
149 | 13 | neels | Each project can be configured to a specific merge strategy, but unfortunately you can't |
150 | decide on a strategy per patch submission. |
||
151 | |||
152 | It seems that the "Merge if Necessary" strategy is best supported, but it creates non-linear |
||
153 | history with numerous merge commits that are usually not at all necessary. |
||
154 | |||
155 | Instead, the "Cherry Pick" strategy puts each patch onto current master's HEAD to create |
||
156 | linear history. However, this will cause merge failures as soon as one patch depends on |
||
157 | another submitted patch, as typical for a feature branch submission. |
||
158 | |||
159 | 1 | zecke | So we prefer the "Rebase if Necessary" strategy, which always tries to apply your patches to |
160 | 13 | neels | the current master HEAD, in sequence with the previous patches on the same branch. |
161 | However, some problems still remain, including some bugs in "Rebase if Necessary". |
||
162 | 1 | zecke | |
163 | 13 | neels | There's a problem with "Rebase if Necessary": If your branch sits at master's HEAD, Gerrit |
164 | refuses to accept the submission, because it thinks that no new changes are submitted. |
||
165 | This is a bug in Gerrit, which holger has fixed manually in our Gerrit installation: |
||
166 | 1 | zecke | |
167 | https://bugs.chromium.org/p/gerrit/issues/detail?id=4158 |
||
168 | |||
169 | |||
170 | 16 | neels | h2. Private Branches: Create a new change for every commit... |
171 | 1 | zecke | |
172 | 13 | neels | Say you have an extensive feature in development, and you want to keep it on the |
173 | upstream git repository to a) keep it safe and b) collaborate with other devs on it. |
||
174 | 16 | neels | So, of course, you have regularly pushed to refs/heads/yoyodyne/feature. |
175 | 13 | neels | |
176 | Since you have the gerrit commit hook installed, your feature branch already has |
||
177 | Change-Id tags in all commit log messages. |
||
178 | |||
179 | Now your feature is complete and you would like to submit it to master. |
||
180 | Alas, Gerrit refuses to accept your patch submission for master, because it |
||
181 | knows the Change-Ids are also on a different branch. |
||
182 | |||
183 | 16 | neels | Gerrit by default enforces that a Change-Id must be unique across all branches, |
184 | so that each submission for review is separate for each branch. Instead, we |
||
185 | want to handle Change-Ids per-branch, so that you can have the same change |
||
186 | submitted to different branches, as separate patch submissions, without having |
||
187 | to cosmetically adjust the Change-Id. |
||
188 | 13 | neels | |
189 | 16 | neels | Solution: set the option |
190 | _Create a new change for every commit not in the target branch_ to _TRUE_ |
||
191 | 13 | neels | |
192 | 20 | neels | h2. Allow content merges |
193 | 14 | neels | |
194 | By default, gerrit compares patches only by the files' paths. If two paths are the same, |
||
195 | it immediately shows them as conflicts (path conflicts). |
||
196 | |||
197 | In software development, a conflict usually means an actual content conflict, so if the |
||
198 | edits are in two entirely separate places in the file, we don't consider this a conflict. |
||
199 | |||
200 | 23 | neels | By setting _Allow content merges_ to _TRUE_ in the git project config, we tell Gerrit to |
201 | 14 | neels | perform text merges of the submitted patches and only complain about actual content |
202 | conflicts, in the usual software engineering sense. |