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1 # Git Cookbook
2
1 A collection of git recipes to do common git tasks. 3 A collection of git recipes to do common git tasks.
2 4
3 See also UsingGit and GitTips. 5 See also [Git Tips](git_tips.md).
4 6
5 7 [TOC]
6
7 8
8 ## Introduction 9 ## Introduction
9 10
10 This is designed to be a cookbook for common command sequences/tasks relating to git, git-cl, and how they work with chromium development. It might be a little light on explanations. 11 This is designed to be a cookbook for common command sequences/tasks relating to
12 git, git-cl, and how they work with chromium development. It might be a little
13 light on explanations.
11 14
12 If you are new to git, or do not have much experience with a distributed version control system, you should also check out [The Git Community Book](http://book. git-scm.com/) for an overview of basic git concepts and general git usage. Know ing what git means by branches, commits, reverts, and resets (as opposed to what SVN means by them) will help make the following much more understandable. 15 If you are new to git, or do not have much experience with a distributed version
16 control system, you should also check out
17 [The Git Community Book](http://book.git-scm.com/) for an overview of basic git
18 concepts and general git usage. Knowing what git means by branches, commits,
19 reverts, and resets (as opposed to what SVN means by them) will help make the
20 following much more understandable.
13 21
14 ## Excluding file(s) from git-cl, while preserving them for later use 22 ## Excluding file(s) from git-cl, while preserving them for later use
15 23
16 Since git-cl assumes that the diff between your current branch and its tracking branch (defaults to the svn-trunk if there is no tracking branch) is what should be used for the CL, the goal is to remove the unwanted files from the current b ranch, and preserve them in another branch, or a similar. 24 Since git-cl assumes that the diff between your current branch and its tracking
25 branch (defaults to the svn-trunk if there is no tracking branch) is what should
26 be used for the CL, the goal is to remove the unwanted files from the current
27 branch, and preserve them in another branch, or a similar.
17 28
18 ### Method #1: Reset your current branch, and selectively commit files. 29 ### Method #1: Reset your current branch, and selectively commit files.
19 30
20 1. `git log` # see the list of your commits. Find the hash of the last commi t before your changes. 31 1. `git log` See the list of your commits. Find the hash of the last commit
21 1. `git reset --soft abcdef` # where abcdef is the hash found in the step abo ve. 32 before your changes.
22 1. `git commit <files_for_this_cl> -m "files to upload"` # commit the files y ou want included in the CL here. 33 1. `git reset --soft abcdef` where abcdef is the hash found in the step above.
23 1. `git checkout -b new_branch_name origin/trunk` # Create a new branch for the files that you want to exclude. 34 1. `git commit <files_for_this_cl> -m "files to upload"` commit the files you
24 1. `git commit -a -m "preserved files"` # Commit the rest of the files. 35 want included in the CL here.
36 1. `git checkout -b new_branch_name origin/trunk` Create a new branch for the
37 files that you want to exclude.
38 1. `git commit -a -m "preserved files"` Commit the rest of the files.
25 39
26 ### Method #2: Create a new branch, reset, then commit files to preserve 40 ### Method #2: Create a new branch, reset, then commit files to preserve
27 This method creates a new branch from your current one to preserve your changes. The commits on the new branch are undone, and then only the files you want to preserve are recommitted.
28 41
29 1. `git checkout -b new_branch_name` # This preserves your old files. 42 This method creates a new branch from your current one to preserve your changes.
30 1. `git log` # see the list of your commits. Find the hash of the last commi t before your changes. 43 The commits on the new branch are undone, and then only the files you want to
31 1. `git reset --soft abcdef` # where abcdef is the hash found in the step abo ve. 44 preserve are recommitted.
32 1. `git commit <files_to_preserve> -m "preserved files"` # commit the found f iles into the new\_branch\_name.
33 45
34 Then revert your files however you'd like in your old branch. The files listed in step 4 will be saved in new\_branch\_name 46 1. `git checkout -b new_branch_name` This preserves your old files.
47 1. `git log` See the list of your commits. Find the hash of the last commit
48 before your changes.
49 1. `git reset --soft abcdef` Where abcdef is the hash found in the step above.
50 1. `git commit <files_to_preserve> -m "preserved files"` Commit the found files
51 into the `new_branch_name`.
52
53 Then revert your files however you'd like in your old branch. The files listed
54 in step 4 will be saved in `new_branch_name`
35 55
36 ### Method #3: Cherry pick changes into review branches 56 ### Method #3: Cherry pick changes into review branches
37 If you are systematic in creating separate local commits for independent changes , you can make a number of different changes in the same client and then cherry- pick each one into a separate review branch.
38 57
39 1. Make and commit a set of independent changes. 58 If you are systematic in creating separate local commits for independent
40 1. `git log` # see the hashes for each of your commits. 59 changes, you can make a number of different changes in the same client and then
41 1. repeat checkout, cherry-pick, upload steps for each change1..n 60 cherry-pick each one into a separate review branch.
42 1. `git checkout -b review-changeN origin` # create a new review branch tra cking origin
43 1. `git cherry-pick <hash of change N>`
44 1. `git cl upload`
45 61
46 If a change needs updating due to review comments, you can go back to your main working branch, update the commit, and re-cherry-pick it into the review branch. 62 1. Make and commit a set of independent changes.
63 1. `git log` # see the hashes for each of your commits.
64 1. repeat checkout, cherry-pick, upload steps for each change1..n
65 1. `git checkout -b review-changeN origin` Create a new review branch
66 tracking origin
67 1. `git cherry-pick <hash of change N>`
68 1. `git cl upload`
47 69
48 1. `git checkout <working branch>` 70 If a change needs updating due to review comments, you can go back to your main
49 1. Make changes. 71 working branch, update the commit, and re-cherry-pick it into the review branch.
50 1. If the commit you want to update is the most recent one: 72
51 1. `git commit --amend <files>` 73 1. `git checkout <working branch>`
52 1. If not: 74 1. Make changes.
53 1. `git commit <files>` 75 1. If the commit you want to update is the most recent one:
54 1. `git rebase -i origin` # use interactive rebase to squash the new commit into the old one. 76 1. `git commit --amend <files>`
55 1. `git log` # observe new hash for the change 77 1. If not:
56 1. `git checkout review-changeN` 78 1. `git commit <files>`
57 1. `git reset --hard` # remove the previous version of the change 79 1. `git rebase -i origin` # use interactive rebase to squash the new
58 1. `cherry-pick <new hash of change N>` 80 commit into the old one.
59 1. `git cl upload` 81 1. `git log` # observe new hash for the change
82 1. `git checkout review-changeN`
83 1. `git reset --hard` # remove the previous version of the change
84 1. `cherry-pick <new hash of change N>`
85 1. `git cl upload`
60 86
61 ## Sharing code between multiple machines 87 ## Sharing code between multiple machines
88
62 Assume Windows computer named vista, Linux one named penguin. 89 Assume Windows computer named vista, Linux one named penguin.
63 Prerequisite: both machine have git clones of the main git tree. 90 Prerequisite: both machine have git clones of the main git tree.
64 ``` 91
92 ```shell
65 vista$ git remote add linux ssh://penguin/path/to/git/repo 93 vista$ git remote add linux ssh://penguin/path/to/git/repo
66 vista$ git fetch linux 94 vista$ git fetch linux
67 vista$ git branch -a # should show "linux/branchname" 95 vista$ git branch -a # should show "linux/branchname"
68 vista$ git checkout -b foobar linux/foobar 96 vista$ git checkout -b foobar linux/foobar
69 vista$ hack hack hack; git commit -a 97 vista$ hack hack hack; git commit -a
70 vista$ git push linux # push branch back to linux 98 vista$ git push linux # push branch back to linux
71 penguin$ git reset --hard # update with new stuff in branch 99 penguin$ git reset --hard # update with new stuff in branch
72 ``` 100 ```
73 101
74 Note that, by default, `gclient sync` will update all remotes. If your other mac hine (i.e., `penguin` in the above example) is not always available, `gclient sy nc` will timeout and fail trying to reach it. To fix this, you may exclude your machine from being fetched by default: 102 Note that, by default, `gclient sync` will update all remotes. If your other
103 machine (i.e., `penguin` in the above example) is not always available,
104 `gclient sync` will timeout and fail trying to reach it. To fix this, you may
105 exclude your machine from being fetched by default:
75 106
76 ``` 107 vista$ git config --bool remote.linux.skipDefaultUpdate true
77 vista$ git config --bool remote.linux.skipDefaultUpdate true
78 ```
79 108
80 ## Reverting and undoing reverts 109 ## Reverting and undoing reverts
110
81 Two commands to be familiar with: 111 Two commands to be familiar with:
82 * `git cherry-pick X` -- patch in the change made in revision X (where X is a hash, or HEAD~2, or whatever)
83 * `git revert X` -- patch in the **inverse** of the change made
84 112
85 With that in hand, say you learned that the commit `abcdef` you just made was ba d. 113 * `git cherry-pick X` -- patch in the change made in revision X (where X is a
114 hash, or HEAD~2, or whatever).
115 * `git revert X` -- patch in the **inverse** of the change made.
116
117 With that in hand, say you learned that the commit `abcdef` you just made was
118 bad.
86 119
87 Revert it locally: 120 Revert it locally:
88 ``` 121
89 $ git checkout origin # start with trunk 122 ```shell
90 $ git show abcdef # grab the svn revision that abcdef was 123 git checkout origin # start with trunk
91 $ git revert abcdef 124 git show abcdef # grab the svn revision that abcdef was
125 git revert abcdef
92 # an editor will pop up; be sure to replace the unhelpful git hash 126 # an editor will pop up; be sure to replace the unhelpful git hash
93 # in the commit message with the svn revision number 127 # in the commit message with the svn revision number
94 ``` 128 ```
95 129
96 Commit the revert: 130 Commit the revert:
97 ``` 131
132 ```shell
98 # note that since "git svn dcommit" commits each local change separately, be 133 # note that since "git svn dcommit" commits each local change separately, be
99 # extra sure that your commit log looks exactly like what you want the tree's co mmit 134 # extra sure that your commit log looks exactly like what you want the tree's
100 # log to look like before you do this. 135 # commit log to look like before you do this.
101 $ git log # double check that the commit log is *exactly* what you wan t 136 git log # double check that the commit log is *exactly* what you want
102 $ git svn dcommit # commit to svn, bypassing all precommit checks and prompts 137 git svn dcommit # commit to svn, bypassing all precommit checks and prompts
103 ``` 138 ```
104 139
105 Roll it forward again locally: 140 Roll it forward again locally:
106 ```
107 $ git checkout mybranch # go back to your old branch again, and
108 $ git reset --hard origin # reset the branch to origin, which now has your rev ert.
109 141
110 $ git cherry-pick abcdef # re-apply your bad change 142 ```shell
111 $ git show # grab the rietveld issue number out of the old comm it 143 # go back to your old branch again, and reset the branch to origin, which now
112 $ git cl issue 12345 # restore the rietveld issue that was cleared on com mit 144 # has your revert.
145 git checkout mybranch
146 git reset --hard origin
147
148
149 git cherry-pick abcdef # re-apply your bad change
150 git show # grab the rietveld issue number out of the old commit
151 git cl issue 12345 # restore the rietveld issue that was cleared on commit
113 ``` 152 ```
114 153
115 And now you can continue hacking where you left off, and since you're reusing th e Reitveld issue you don't have to rewrite the commit message. (You may want to go manually reopen the issue on the Rietveld site -- `git cl status` will give you the URL.) 154 And now you can continue hacking where you left off, and since you're reusing
155 the Reitveld issue you don't have to rewrite the commit message. (You may want
156 to go manually reopen the issue on the Rietveld site -- `git cl status` will
157 give you the URL.)
116 158
117 ## Retrieving, or diffing against an old file revision 159 ## Retrieving, or diffing against an old file revision
118 Git works in terms of commits, not files. Thus, working with the history of a si ngle file requires modified version of the show and diff commands. 160
119 ``` 161 Git works in terms of commits, not files. Thus, working with the history of a
120 $ git log path/to/file # Find the commit you want in the file's comm it log. 162 single file requires modified version of the show and diff commands.
121 $ git show 123abc:path/to/file # This prints out the file contents at commit 123abc. 163
122 $ git diff 123abc -- path/to/file # Diff the current version against path/to/fi le 164 ```shell
123 # against the version at path/to/file 165 # Find the commit you want in the file's commit log.
166 git log path/to/file
167 # This prints out the file contents at commit 123abc.
168 git show 123abc:path/to/file
169 # Diff the current version against path/to/file against the version at
170 # path/to/file
171 git diff 123abc -- path/to/file
124 ``` 172 ```
125 173
126 When invoking `git show` or `git diff`, the `path/to/file` is **not relative the the current directory**. It must be the full path from the directory where the .git directory lives. This is different from invoking `git log` which understan ds relative paths. 174 When invoking `git show` or `git diff`, the `path/to/file` is **not relative the
175 the current directory**. It must be the full path from the directory where the
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176 .git directory lives. This is different from invoking `git log` which
177 understands relative paths.
127 178
128 ## Checking out pristine branch from git-svn 179 ## Checking out pristine branch from git-svn
129 In the backend, git-svn keeps a remote tracking branch that points to the the co mmit tree representing the svn repository. The name of this branch is configure d during `git svn init`. The git-svn remote branch is often named `origin/trunk ` for Chromium, and `origin/master` for WebKit.
130 180
131 If you want to checkout a "fresh" branch, you can base it directly off the remot e branch for svn. 181 In the backend, git-svn keeps a remote tracking branch that points to the the
182 commit tree representing the svn repository. The name of this branch is
183 configured during `git svn init`. The git-svn remote branch is often named
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184 `origin/trunk` for Chromium, and `origin/master` for WebKit.
132 185
133 ``` 186 If you want to checkout a "fresh" branch, you can base it directly off the
134 $ git checkout -b fresh origin/trunk # Replace with origin/master for webkit. 187 remote branch for svn.
135 ```
136 188
137 To find out what your git-svn remote branch name is, you can examine your `.git/ config` file and look for the `svn-remote` entry. It will look something like t his: 189 git checkout -b fresh origin/trunk # Replace with origin/master for webkit.
190
191
192 To find out what your git-svn remote branch name is, you can examine your
193 `.git/config` file and look for the `svn-remote` entry. It will look something
194 like this:
138 195
139 ``` 196 ```
140 [svn-remote "svn"] 197 [svn-remote "svn"]
141 url = svn://svn.chromium.org/chrome 198 url = svn://svn.chromium.org/chrome
142 fetch = trunk/src:refs/remotes/origin/trunk 199 fetch = trunk/src:refs/remotes/origin/trunk
143 ``` 200 ```
144 201
145 The last line (`fetch = trunk/src:refs/remotes/origin/trunk`), says to make `tru nk/src` on svn into `refs/remote/origin/trunk` in the local git checkout. Which means, the name of the svn remote branch name is `origin/trunk`. You can use t his branch name for all sorts of actions (diff, log, show, etc.) 202 The last line (`fetch = trunk/src:refs/remotes/origin/trunk`), says to make
203 `trunk/src` on svn into `refs/remote/origin/trunk` in the local git checkout.
204 Which means, the name of the svn remote branch name is `origin/trunk`. You can
205 use this branch name for all sorts of actions (diff, log, show, etc.)
146 206
147 ## Making your `git svn {fetch,rebase}` go fast 207 ## Making your `git svn {fetch,rebase}` go fast
148 If you are pulling changes from the git repository in Chromium (or webkit), but your your `git svn` commands still seem to pull each change individually from sv n, your repository is probably setup incorrectly. Make sure the entries in your `.git/config` look something like this: 208
209 If you are pulling changes from the git repository in Chromium (or WebKit), but
210 your your `git svn` commands still seem to pull each change individually from
211 svn, your repository is probably setup incorrectly. Make sure the entries in
212 your `.git/config` look something like this:
149 213
150 ``` 214 ```
151 [remote "origin"] 215 [remote "origin"]
152 url = https://chromium.googlesource.com/chromium/src.git 216 url = https://chromium.googlesource.com/chromium/src.git
153 fetch = +refs/heads/*:refs/remotes/origin/* 217 fetch = +refs/heads/*:refs/remotes/origin/*
154 [svn-remote "svn"] 218 [svn-remote "svn"]
155 url = svn://svn.chromium.org/chrome 219 url = svn://svn.chromium.org/chrome
156 fetch = trunk/src:refs/remotes/origin/trunk 220 fetch = trunk/src:refs/remotes/origin/trunk
157 ``` 221 ```
158 222
159 Here, `git svn fetch` will update the hash in refs/remotes/origin/trunk as per t he `fetch =` line under `svn-remote`. Similarly, `git fetch` will update the ** same** tag under `refs/remotes/origin`. 223 Here, `git svn fetch` will update the hash in refs/remotes/origin/trunk as per
224 the `fetch =` line under `svn-remote`. Similarly, `git fetch` will update the
225 **same** tag under `refs/remotes/origin`.
160 226
161 With this setup, `git fetch` will use the faster git protocol to pull changes do wn into `origin/trunk`. This effectively updates the high-water mark for `git-sv n`. Later invocations of `git svn {find-rev, fetch, rebase}` will be be able to skip pulling those revisions down from the svn server. Instead, it will just r un a regex over the commit log in `origin/trunk` and parse all the `git-svn-id` lines. To rebuild the mapping. Example: 227 With this setup, `git fetch` will use the faster git protocol to pull changes
228 down into `origin/trunk`. This effectively updates the high-water mark for
229 `git-svn`. Later invocations of `git svn {find-rev, fetch, rebase}` will be be
230 able to skip pulling those revisions down from the svn server. Instead, it
231 will just run a regex over the commit log in `origin/trunk` and parse all the
232 `git-svn-id` lines. To rebuild the mapping. Example:
162 233
163 ``` 234 ```
164 commit 016d28b8c4959a3d28d2fbfb4b86c0361aad74ef 235 commit 016d28b8c4959a3d28d2fbfb4b86c0361aad74ef
165 Author: mpcomplete@chromium.org <mpcomplete@chromium.org@0039d316-1c4b-4281-b951 -d872f2087c98> 236 Author: mpcomplete@chromium.org <mpcomplete@chromium.org@0039d316-1c4b-4281-b951 -d872f2087c98>
166 Date: Mon Jul 19 19:09:41 2010 +0000 237 Date: Mon Jul 19 19:09:41 2010 +0000
167 238
168 Revert r42636. That hack is no longer needed now that we removed the compact 239 Revert r42636. That hack is no longer needed now that we removed the compact
169 location bar view. 240 location bar view.
170 241
171 BUG=38992 242 BUG=38992
172 243
173 Review URL: http://codereview.chromium.org/3036004 244 Review URL: http://codereview.chromium.org/3036004
174 245
175 git-svn-id: svn://svn.chromium.org/chrome/trunk/src@52935 0039d316-1c4b-4281 -b951-d872f2087c98 246 git-svn-id: svn://svn.chromium.org/chrome/trunk/src@52935 0039d316-1c4b-4281 -b951-d872f2087c98
176 ``` 247 ```
177 248
178 Will be parsed to map svn revision r52935 (on Google Code) to commit 016d28b8c49 59a3d28d2fbfb4b86c0361aad74ef. The parsing will generate a lot of lines that lo ok like `rXXXX = 01234ABCD`. It should generally take a minute or so when doing an incremental update. 249 Will be parsed to map svn revision r52935 (on Google Code) to commit
250 016d28b8c4959a3d28d2fbfb4b86c0361aad74ef. The parsing will generate a lot of
251 lines that look like `rXXXX = 01234ABCD`. It should generally take a minute or
252 so when doing an incremental update.
179 253
180 For this to work, two things must be true: 254 For this to work, two things must be true:
181 255
182 * The svn url in the `svn-remote` clause must exactly match the url in the git -svn-id pulled form the server. 256 * The svn url in the `svn-remote` clause must exactly match the url in the
183 * The fetch from origin must write into the exact same branch that specified i n the fetch line of `svn-remote`. 257 git-svn-id pulled form the server.
258 * The fetch from origin must write into the exact same branch that specified
259 in the fetch line of `svn-remote`.
184 260
185 If either of these are not true, then `git svn fetch` and friends will talk to s vn directly, and be very slow. 261 If either of these are not true, then `git svn fetch` and friends will talk to
262 svn directly, and be very slow.
186 263
187 ## Reusing a Git mirror 264 ## Reusing a Git mirror
188 265
189 If you have a nearby copy of a Git repo, you can quickly bootstrap your copy fro m that one then adjust it to point it at the real upstream one. 266 If you have a nearby copy of a Git repo, you can quickly bootstrap your copy
267 from that one then adjust it to point it at the real upstream one.
190 268
191 1. Clone a nearby copy of the code you want: `git clone coworker-machine:/path /to/repo` 269 1. Clone a nearby copy of the code you want: `git clone coworker-machine:/path/ to/repo`
192 1. Change the URL your copy fetches from to point at the real git repo: `git s et-url origin http://src.chromium.org/git/chromium.git` 270 1. Change the URL your copy fetches from to point at the real git repo:
193 1. Update your copy: `git fetch` 271 `git set-url origin http://src.chromium.org/git/chromium.git`
194 1. Delete any extra branches that you picked up in the initial clone: `git pru ne origin` 272 1. Update your copy: `git fetch`
273 1. Delete any extra branches that you picked up in the initial clone:
274 `git prune origin`
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