Gerrit » History » Version 35
neels, 07/12/2016 12:59 PM
1 | 1 | zecke | h1. Contributing using Gerrit |
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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. |
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11 | * patches are build-tested (and possibly even further tested) by jenkins before they are applied |
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12 | * developers + maintainers can formally vote on a patch (developer: -1/0/+1, maintainer: -2/0/+2) |
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13 | * once a patch has +2 score, it can be (automatically) merged into master |
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14 | * patch sumissions not via git send-email but direcly from git |
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15 | |||
16 | h2. Osmocom Subprojects using Gerrit |
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17 | |||
18 | 1 | zecke | The following projects use Gerrit to contribute changes: |
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20 | * libosmocore.git |
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21 | * libosmo-abis.git |
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22 | * libosmo-netif.git |
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23 | * libosmo-sccp.git |
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24 | * libsmpp34.git |
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25 | * openbsc.git |
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26 | * osmo-bts.git |
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27 | * osmo-iuh.git |
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28 | * osmo-pcu.git |
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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. |
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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). |
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37 | |||
38 | After the initial sign-up you will need to: |
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39 | 1 | zecke | |
40 | * Pick a username (can not be changed) |
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41 | * Add your public ssh key(s) |
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42 | * Add email addresses you intend to use as author/comitter |
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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. |
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45 | Please send a short requesting email to openbsc@lists.osmocom.org. |
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46 | 1 | zecke | |
47 | h2. Setting up Gerrit for commits and pushing |
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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, |
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51 | so when you checkout a new branch you have to supply the remote explicitly (cumbersome). |
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52 | 34 | neels | The gerrit repositories and git.osmocom.org are constantly synced, so it is sufficient |
53 | to clone from gerrit only. |
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54 | 33 | neels | |
55 | h3. Simplest: new clone |
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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 |
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59 | 33 | neels | <pre> |
60 | git clone ssh://$USERNAME@gerrit.osmocom.org:29418/$PROJECT.git |
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61 | scp -P 29418 $USERNAME@gerrit.osmocom.org:hooks/commit-msg $PROJECT/.git/hooks/ |
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62 | </pre> |
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63 | |||
64 | h3. SSH config |
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65 | |||
66 | In '~/.ssh/config', add these lines: |
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67 | <pre> |
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68 | Host foo |
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69 | Hostname gerrit.osmocom.org |
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70 | Port 29418 |
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71 | User $USERNAME |
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72 | </pre> |
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73 | (replace 'foo' with your favorite shortcut name, |
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74 | replace '$USERNAME' with your user name as used on the gerrit website) |
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75 | |||
76 | Then you can shorten above commands to |
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77 | 1 | zecke | <pre> |
78 | 33 | neels | git clone ssh://foo/$PROJECT.git |
79 | 35 | neels | scp foo:hooks/commit-msg $PROJECT/.git/hooks/ |
80 | 33 | neels | </pre> |
81 | |||
82 | |||
83 | h3. Add gerrit to an existing clone |
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84 | |||
85 | 7 | neels | * Add the remote to be able to fetch and push to gerrit |
86 | * Fetch the commit hook that adds Change-Id to each commit to uniquely identify a commit |
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87 | |||
88 | <pre> |
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89 | USERNAME=gerrit_user_name |
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90 | PROJECT=$(basename $PWD) |
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91 | git remote add gerrit ssh://$USERNAME@gerrit.osmocom.org:29418/$PROJECT.git |
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92 | scp -P 29418 $USERNAME@gerrit.osmocom.org:hooks/commit-msg .git/hooks/ |
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93 | </pre> |
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94 | |||
95 | * In case your local username matches the gerrit username, the setup shortens to |
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96 | |||
97 | <pre> |
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98 | PROJECT=$(basename $PWD) |
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99 | git remote add gerrit ssh://gerrit.osmocom.org:29418/$PROJECT.git |
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100 | scp -P 29418 gerrit.osmocom.org:hooks/commit-msg .git/hooks/ |
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101 | </pre> |
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102 | 1 | zecke | |
103 | 33 | neels | h2. Push for review |
104 | 7 | neels | |
105 | 31 | neels | <pre> |
106 | 1 | zecke | git push gerrit HEAD:refs/for/master |
107 | </pre> |
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108 | |||
109 | 33 | neels | h2. Push a "private" user branch |
110 | |||
111 | *Note* that you must be a member of the "known users" group, see above. |
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112 | |||
113 | If gerrit is your only remote, and if your local branch name is of the |
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114 | form 'yourname/topic', you can just |
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115 | 1 | zecke | <pre> |
116 | 33 | neels | git push |
117 | 1 | zecke | </pre> |
118 | 33 | neels | (and git will tell you what to do) |
119 | 1 | zecke | |
120 | 33 | neels | If you have other remotes as well, do |
121 | 1 | zecke | <pre> |
122 | 33 | neels | git push gerrit |
123 | 31 | neels | </pre> |
124 | 7 | neels | |
125 | 33 | neels | To push with a "nonstandard" local branch name, do |
126 | <pre> |
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127 | git push gerrit HEAD:refs/heads/$USERNAME/topic |
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128 | </pre> |
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129 | |||
130 | h2. List changesets in gerrit |
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131 | 7 | neels | <pre> |
132 | git ls-remote gerrit changes/* |
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133 | 2 | zecke | </pre> |
134 | 12 | msuraev | |
135 | 17 | neels | h1. Tips and Tricks |
136 | 1 | zecke | |
137 | 17 | neels | h2. Throw-away branch |
138 | |||
139 | 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), |
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140 | make your changes/amendments and than send patch(es) back to gerrit while removing temporary branch automatically with "git review -f". |
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141 | 13 | neels | |
142 | 25 | neels | h2. Re-submit a Branch with Amended Commits |
143 | 13 | neels | |
144 | 1 | zecke | On a feature branch, one typically has numerous commits that depend on their preceding commits. |
145 | 29 | neels | Often, some of the branch commits need to be amended for fixes. But, Gerrit will refuse your branch |
146 | re-submission if the first branch commit is unchanged. |
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147 | 1 | zecke | |
148 | 16 | neels | To re-submit a branch, make sure to cosmetically tweak the branch's first commit log message |
149 | 22 | neels | before each re-submission (keep the Change-Id, really make just a cosmetic change). |
150 | 13 | neels | |
151 | 16 | neels | <pre> |
152 | git rebase -i master |
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153 | # replace the first line's 'pick' with 'r' (or 'reword'), exit editor |
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154 | # git presents you with commit log message, make any tiny modification. |
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155 | 1 | zecke | </pre> |
156 | |||
157 | 29 | neels | The cause: Gerrit refuses to accept a commit with a Change-Id that it already knows and |
158 | where the commit hash is identical. |
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159 | 1 | zecke | |
160 | 29 | neels | If you just cosmetically tweak the first commit's log message, the commit hash |
161 | is changed. Since the following commits contain their predecessor's commit hash, now |
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162 | all of the branch's commit hashes are modified, and gerrit happily accepts them as a |
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163 | new patch set. It will still pick up the Change-Ids (which you shouldn't edit) and |
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164 | notice if commits have remained identical (keeping the votes). But with the minor |
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165 | commit log tweak, it will no longer thwart your re-submission with an error message. |
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166 | |||
167 | Note: you could modify all the Change-Ids, but now your branch submission would |
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168 | open entirely new review entries and you would have to abandon your previous submission. |
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169 | Comments on the first submission are lost and you cannot diff between patch sets. |
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170 | |||
171 | |||
172 | 26 | neels | h2. Re-submit Previously Abandoned Changes |
173 | 16 | neels | |
174 | You have to edit the Change-Ids, on a branch that would be every single commit log message. |
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175 | |||
176 | 13 | neels | <pre> |
177 | 1 | zecke | cd openbsc |
178 | git co my-branch |
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179 | git rebase -i master |
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180 | # replace all 'pick' with 'r' (or 'reword'), exit your editor |
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181 | 13 | neels | # git presents each commit log message for editing |
182 | </pre> |
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183 | |||
184 | 27 | neels | h2. Submit a "private" branch for master |
185 | 21 | neels | |
186 | If you've pushed a branch to refs/heads/* somewhere, gerrit will already know the Change-Ids on it. |
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187 | 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, |
188 | 21 | neels | or gerrit will refuse to accept your submission. |
189 | |||
190 | 16 | neels | h1. Reasons for Particular Configuration |
191 | 13 | neels | |
192 | 16 | neels | h2. Rebase if necessary |
193 | |||
194 | There are different merge strategies that Gerrit performs to accept patches. |
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195 | 13 | neels | Each project can be configured to a specific merge strategy, but unfortunately you can't |
196 | decide on a strategy per patch submission. |
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197 | |||
198 | It seems that the "Merge if Necessary" strategy is best supported, but it creates non-linear |
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199 | history with numerous merge commits that are usually not at all necessary. |
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200 | |||
201 | Instead, the "Cherry Pick" strategy puts each patch onto current master's HEAD to create |
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202 | linear history. However, this will cause merge failures as soon as one patch depends on |
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203 | another submitted patch, as typical for a feature branch submission. |
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204 | |||
205 | 1 | zecke | So we prefer the "Rebase if Necessary" strategy, which always tries to apply your patches to |
206 | 13 | neels | the current master HEAD, in sequence with the previous patches on the same branch. |
207 | However, some problems still remain, including some bugs in "Rebase if Necessary". |
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208 | 1 | zecke | |
209 | 13 | neels | There's a problem with "Rebase if Necessary": If your branch sits at master's HEAD, Gerrit |
210 | refuses to accept the submission, because it thinks that no new changes are submitted. |
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211 | This is a bug in Gerrit, which holger has fixed manually in our Gerrit installation: |
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212 | 1 | zecke | |
213 | https://bugs.chromium.org/p/gerrit/issues/detail?id=4158 |
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214 | |||
215 | |||
216 | 16 | neels | h2. Private Branches: Create a new change for every commit... |
217 | 1 | zecke | |
218 | 13 | neels | Say you have an extensive feature in development, and you want to keep it on the |
219 | upstream git repository to a) keep it safe and b) collaborate with other devs on it. |
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220 | 16 | neels | So, of course, you have regularly pushed to refs/heads/yoyodyne/feature. |
221 | 13 | neels | |
222 | Since you have the gerrit commit hook installed, your feature branch already has |
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223 | Change-Id tags in all commit log messages. |
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224 | |||
225 | Now your feature is complete and you would like to submit it to master. |
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226 | Alas, Gerrit refuses to accept your patch submission for master, because it |
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227 | knows the Change-Ids are also on a different branch. |
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228 | |||
229 | 16 | neels | Gerrit by default enforces that a Change-Id must be unique across all branches, |
230 | so that each submission for review is separate for each branch. Instead, we |
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231 | want to handle Change-Ids per-branch, so that you can have the same change |
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232 | submitted to different branches, as separate patch submissions, without having |
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233 | to cosmetically adjust the Change-Id. |
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234 | 13 | neels | |
235 | 16 | neels | Solution: set the option |
236 | _Create a new change for every commit not in the target branch_ to _TRUE_ |
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237 | 13 | neels | |
238 | 20 | neels | h2. Allow content merges |
239 | 14 | neels | |
240 | By default, gerrit compares patches only by the files' paths. If two paths are the same, |
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241 | it immediately shows them as conflicts (path conflicts). |
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242 | |||
243 | In software development, a conflict usually means an actual content conflict, so if the |
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244 | edits are in two entirely separate places in the file, we don't consider this a conflict. |
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245 | |||
246 | 23 | neels | By setting _Allow content merges_ to _TRUE_ in the git project config, we tell Gerrit to |
247 | 14 | neels | perform text merges of the submitted patches and only complain about actual content |
248 | conflicts, in the usual software engineering sense. |
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249 | 32 | neels | |
250 | h1. Admin |
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251 | |||
252 | h2. Adding users to groups |
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253 | |||
254 | Normally, the gerrit UI auto-completes a user name in the edit field. It has happened |
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255 | though that an existing user is not auto-completed, as if it didn't exist. In that case, |
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256 | find out the user ID (seven digit number like 1000123) and just enter that. |
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257 | |||
258 | The user ID can be found on the user's "Settings" page, or in the database (s.b.). |
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259 | |||
260 | h2. Querying the database directly |
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261 | |||
262 | If your user has permission to access the database, you can place SQL queries using the |
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263 | 'gerrit gsql' commands over ssh: |
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264 | |||
265 | <pre> |
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266 | ssh -p 29418 $USERNAME@gerrit.osmocom.org 'gerrit gsql --format PRETTY -c "show tables"' |
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267 | ssh -p 29418 $USERNAME@gerrit.osmocom.org 'gerrit gsql --format PRETTY -c "select full_name,account_id from accounts"' |
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268 | </pre> |
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269 | |||
270 | This seems to be the MySQL dialect. |