├── .gitignore ├── LICENSE └── README.md /.gitignore: -------------------------------------------------------------------------------- 1 | # Compiled Object files, Static and Dynamic libs (Shared Objects) 2 | *.o 3 | *.a 4 | *.so 5 | 6 | # Folders 7 | _obj 8 | _test 9 | 10 | # Architecture specific extensions/prefixes 11 | *.[568vq] 12 | [568vq].out 13 | 14 | *.cgo1.go 15 | *.cgo2.c 16 | _cgo_defun.c 17 | _cgo_gotypes.go 18 | _cgo_export.* 19 | 20 | _testmain.go 21 | 22 | *.exe 23 | *.test 24 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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Interpretation of Sections 15 and 16. 613 | 614 | If the disclaimer of warranty and limitation of liability provided 615 | above cannot be given local legal effect according to their terms, 616 | reviewing courts shall apply local law that most closely approximates 617 | an absolute waiver of all civil liability in connection with the 618 | Program, unless a warranty or assumption of liability accompanies a 619 | copy of the Program in return for a fee. 620 | 621 | END OF TERMS AND CONDITIONS 622 | 623 | How to Apply These Terms to Your New Programs 624 | 625 | If you develop a new program, and you want it to be of the greatest 626 | possible use to the public, the best way to achieve this is to make it 627 | free software which everyone can redistribute and change under these terms. 628 | 629 | To do so, attach the following notices to the program. It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | {one line to give the program's name and a brief idea of what it does.} 635 | Copyright (C) {year} {name of author} 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | {project} Copyright (C) {year} {fullname} 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | example-go-app 2 | ============== 3 | 4 | This is a follow-along example of my preferred way to maintain 5 | dependencies for a Go (golang) project using git subtree. 6 | 7 | Introduction 8 | ============ 9 | 10 | There are many ways to build and maintain a Go project that requires 11 | external libraries. 12 | 13 | The simplest way (which is already built into the Go toolchain itself) 14 | is to just run `go get` on all your dependencies, and hope that the 15 | library authors don't ever introduce breaking changes into their code. 16 | For small and personal projects that is fine, but for people who are 17 | writing code for a living, that isn't nearly good enough. 18 | 19 | There are many tools that have sprouted up among the Go community for 20 | managing library dependencies. You can visit the [Go 21 | Wiki](https://code.google.com/p/go-wiki/wiki/PackageManagementTools) 22 | for some of the popular ones. 23 | 24 | However, for my work, I don't wish to use any of those tools, and 25 | furthermore I want to use a dependency management scheme that is not 26 | Go-specific. 27 | 28 | My DVCS of choice is [`git`](http://www.git-scm.org), and recent 29 | versions of git now have the [`git 30 | subtree`](http://blogs.atlassian.com/2013/05/alternatives-to-git-submodule-git-subtree/) 31 | command which makes working with separate library projects smoother than 32 | before (definitely so compared to using the `git submodule` command). 33 | 34 | This project is intended to be an example of my preferred workflow 35 | with Go and `git subtree` which makes things relatively easy for the 36 | other developers on my team, and still allows us to contribute changes 37 | back to the upstream authors. 38 | 39 | Development Scenario 40 | ==================== 41 | 42 | We're going to be writing a small application for our company 43 | 'example.com', and we're going to need a couple of different libraries 44 | for this project. 45 | 46 | In one case, with the [upsilon 47 | project](https://github.com/jamesgraves/upsilon), we don't anticipate 48 | needing to make any major changes to the library, we will definitely 49 | want to stay up-to-date with improvements to it, and we will probably 50 | just be contributing bugfixes back to the upstream author. 51 | 52 | The other library is 53 | [omicron](https://github.com/jamesgraves/omicron), and we've decided 54 | to fork it, because we're planning on making incompatible changes to 55 | it. 56 | 57 | I've already forked these two projects on GitHub, and if you're 58 | following along, you will want to do the same under your own account. 59 | Of course you'll then need to adjust the repository paths that follow. 60 | 61 | 62 | Initial Checkout 63 | ================ 64 | 65 | 66 | ``` 67 | $ mkdir myproject 68 | $ cd myproject 69 | $ git clone git@github.com:jamesgraves/example-go-app.git 70 | Cloning into 'example-go-app'... 71 | [...] 72 | Checking connectivity... done. 73 | ``` 74 | 75 | We're going to be using a per-project GOPATH. This is because the 76 | entire project is under version control, and we want to be sure we've 77 | got the exact version of every file that goes into the build. 78 | 79 | We really can't do things like set GOPATH to `${HOME}` as is often 80 | suggested, because we want to make sure all the source code is in the 81 | main project repository. 82 | 83 | 84 | ``` 85 | $ cd example-go-app/ 86 | $ export GOPATH=~/myproject/example-go-app 87 | ``` 88 | 89 | Let's switch to a new branch so that we won't mess up the master 90 | branch used for this example. 91 | 92 | 93 | ``` 94 | $ git checkout working 95 | Branch working set up to track remote branch working from origin. 96 | Switched to a new branch 'working' 97 | $ ls src/example.com/myapp/ 98 | example_main.go 99 | ``` 100 | 101 | In this case, I had already created a `working` branch, so you'd 102 | normally need to run checkout with the `-b` option to create the 103 | branch. 104 | 105 | Let's edit the initial main program, and run it. 106 | 107 | ``` 108 | $ vi src/example.com/myapp/example_main.go 109 | $ cat src/example.com/myapp/example_main.go 110 | package main 111 | 112 | import ( 113 | "fmt" 114 | ) 115 | 116 | func main() { 117 | fmt.Println("This is main.") 118 | } 119 | $ go run src/example.com/myapp/example_main.go 120 | This is main. 121 | ``` 122 | 123 | This is all standard git stuff so far. 124 | 125 | Import Libraries into Our Project 126 | ================================= 127 | 128 | Now it is time to add the remote for the library we're going to fork 129 | and maintain ourselves. 130 | 131 | ``` 132 | $ git remote add -f omicron-vendor git@github.com:jamesgraves/omicron.git 133 | Updating omicron-vendor 134 | warning: no common commits 135 | [...] 136 | From github.com:jamesgraves/omicron 137 | * [new branch] master -> omicron-vendor/master 138 | * [new branch] working -> omicron-vendor/working 139 | ``` 140 | 141 | Don't worry about the 'no common commits', that is to be expected. 142 | 143 | As before, I had already created 'working' branches, so you may want 144 | to do that first. Otherwise, you can push / pull from master in all 145 | the following examples. 146 | 147 | We can now add the library as a subtree in our existing project. 148 | 149 | Since we're going to fork this library, we're going to put it in our 150 | project directory under our own path: 151 | 152 | ``` 153 | $ mkdir -p src/github.com/jamesgraves/ 154 | ``` 155 | 156 | And now bring in the actual source. It isn't necessary to squash the 157 | commits, but it may make it easier to read the history. 158 | 159 | ``` 160 | $ git subtree add --prefix src/github.com/jamesgraves/omicron omicron-vendor master --squash 161 | git fetch omicron-vendor master 162 | From github.com:jamesgraves/omicron 163 | * branch master -> FETCH_HEAD 164 | Added dir 'src/github.com/jamesgraves/omicron' 165 | $ find src -type f -print 166 | src/example.com/myapp/example_main.go 167 | src/github.com/jamesgraves/omicron/LICENSE 168 | src/github.com/jamesgraves/omicron/.gitignore 169 | src/github.com/jamesgraves/omicron/README.md 170 | src/github.com/jamesgraves/omicron/lib.go 171 | ``` 172 | 173 | You may note that there is no .git directory in there, everything is 174 | stored in the main .git directory. 175 | 176 | The omicron library is pretty basic: 177 | 178 | ``` 179 | $ cat src/github.com/jamesgraves/omicron/lib.go 180 | package omicron 181 | 182 | import ( "fmt" ) 183 | 184 | func Foo() { 185 | fmt.Println("This is Foo() from package omicron") 186 | } 187 | ``` 188 | 189 | For the upsilon library that we're only going to make bugfixes to, 190 | we're not going to change the original directory hierarchy. So we 191 | aren't going to change location for where it lives in our project 192 | directory. It is going to end up in the same place as if we had just 193 | run `go get github.com/upstream-author/upsilon` (if upstream-author 194 | actually existed). 195 | 196 | By not changing the directory hierarchy, that reduces the need to 197 | change the import paths of other code that also uses the upsilon 198 | library. 199 | 200 | ``` 201 | $ mkdir -p src/github.com/upstream-author 202 | ``` 203 | 204 | Add the remote of our fork. 205 | 206 | ``` 207 | $ git remote add -f upsilon-vendor git@github.com:jamesgraves/upsilon.git 208 | Updating upsilon-vendor 209 | warning: no common commits 210 | [...] 211 | From github.com:jamesgraves/upsilon 212 | * [new branch] master -> upsilon-vendor/master 213 | ``` 214 | 215 | And pull in its source too. 216 | 217 | ``` 218 | $ git subtree add --prefix src/github.com/upstream-author/upsilon upsilon-vendor master --squash 219 | git fetch upsilon-vendor master 220 | From github.com:jamesgraves/upsilon 221 | * branch master -> FETCH_HEAD 222 | Added dir 'src/github.com/upstream-author/upsilon' 223 | $ ls src/github.com/upstream-author/upsilon 224 | lib.go LICENSE README.md 225 | ``` 226 | 227 | As with the omicron library, upsilon is also somewhat unambitious. 228 | 229 | ``` 230 | $ cat src/github.com/upstream-author/upsilon/lib.go 231 | package upsilon 232 | 233 | import ( "fmt" ) 234 | 235 | func Bar() { 236 | fmt.Println("This is Bar() from package upsilon") 237 | } 238 | ``` 239 | 240 | Let's now edit our main program to use these new and fantastically 241 | complicated libraries. 242 | 243 | ``` 244 | $ vi src/example.com/myapp/example_main.go 245 | $ cat src/example.com/myapp/example_main.go 246 | package main 247 | 248 | import ( 249 | "fmt" 250 | "github.com/jamesgraves/omicron" 251 | "github.com/upstream-author/upsilon" 252 | ) 253 | 254 | func main() { 255 | fmt.Println("This is main.") 256 | omicron.Foo() 257 | upsilon.Bar() 258 | } 259 | $ go run src/example.com/myapp/example_main.go 260 | This is main. 261 | This is Foo() from package omicron 262 | This is Bar() from package upsilon 263 | ``` 264 | 265 | Whew! That was a lot more work than just running `go get`. 266 | 267 | Edit and Push Changes to Libraries 268 | ================================== 269 | 270 | Let's push these imported libraries into our central project 271 | repository to the 'working' branch. 272 | 273 | ``` 274 | $ git status 275 | # On branch working 276 | # Your branch is ahead of 'origin/working' by 4 commits. 277 | # (use "git push" to publish your local commits) 278 | # 279 | # Changes not staged for commit: 280 | # (use "git add ..." to update what will be committed) 281 | # (use "git checkout -- ..." to discard changes in working directory) 282 | # 283 | # modified: src/example.com/myapp/example_main.go 284 | # 285 | no changes added to commit (use "git add" and/or "git commit -a") 286 | $ git commit -m 'Now using omicron and upsilon libs' src/example.com/myapp/example_main.go 287 | [working 926bda2] Now using omicron and upsilon libs 288 | 1 file changed, 4 insertions(+) 289 | $ git push origin working 290 | Counting objects: 25, done. 291 | [...] 292 | Total 25 (delta 4), reused 0 (delta 0) 293 | To git@github.com:jamesgraves/example-go-app.git 294 | e1d5241..926bda2 working -> working 295 | ``` 296 | 297 | Time to make a small bug fix for upsilon, and push that back to our 298 | own example project. 299 | 300 | ``` 301 | $ vi src/github.com/upstream-author/upsilon/lib.go 302 | $ cat src/github.com/upstream-author/upsilon/lib.go 303 | package upsilon 304 | 305 | import ( "fmt" ) 306 | 307 | func Bar() { 308 | fmt.Println("This is Bar() from package upsilon, with a small bugfix.") 309 | } 310 | $ git commit -m 'Bugfix for print.' src/github.com/upstream-author/upsilon/lib.go 311 | [working c4d49fb] Bugfix for print. 312 | 1 file changed, 1 insertion(+), 1 deletion(-) 313 | 314 | git push origin working 315 | Counting objects: 7, done. 316 | [...] 317 | To git@github.com:jamesgraves/example-go-app.git 318 | 926bda2..c4d49fb working -> working 319 | ``` 320 | Note that we haven't pushed our changes back to the library project 321 | itself, just to our application project. 322 | 323 | Since that won't really help the other users of the upsilon library 324 | (because our main project may not be public), we need to push that bug 325 | fix back to our fork of upsilon. 326 | 327 | ``` 328 | $ git subtree push --prefix=src/github.com/upstream-author/upsilon upsilon-vendor working 329 | git push using: upsilon-vendor working 330 | [...] 331 | To git@github.com:jamesgraves/upsilon.git 332 | e8ffa07..f920c4f f920c4f0d3e9df6b3fc52988a192fd39cfa72bb4 -> working 333 | ``` 334 | 335 | So this is going to push the `f920c4f` back to our fork at 336 | `github.com:jamesgraves/upsilon`, and from there we can open a pull 337 | request with upstream-author for this bug fix. 338 | 339 | The situation will be similar for adding new functionality to our fork 340 | of the omicron library. 341 | 342 | ``` 343 | $ vi src/github.com/jamesgraves/omicron/lib.go 344 | $ cat src/github.com/jamesgraves/omicron/lib.go 345 | package omicron 346 | 347 | import ( "fmt" ) 348 | 349 | func Foo() { 350 | fmt.Println("This is Foo() from package omicron.") 351 | fmt.Println("Major new functionality for omicron."); 352 | } 353 | $ git commit -m 'New functionality.' src/github.com/jamesgraves/omicron/lib.go 354 | [working 6f8ced7] New functionality. 355 | 1 file changed, 2 insertions(+), 1 deletion(-) 356 | $ git push origin working 357 | Counting objects: 7, done. 358 | [...] 359 | To git@github.com:jamesgraves/example-go-app.git 360 | c4d49fb..6f8ced7 working -> working 361 | ``` 362 | 363 | And finally we can push our new functionality to our fork of omicron 364 | so that other users of our version of the omicron library can easily get 365 | it too. 366 | 367 | ``` 368 | $ git subtree push --prefix=src/github.com/jamesgraves/omicron omicron-vendor working 369 | git push using: omicron-vendor working 370 | [...] 371 | To git@github.com:jamesgraves/omicron.git 372 | 5808bb0..ef181b9 ef181b96c7155e126310df11ac2b887d7747e9c0 -> working 373 | ``` 374 | 375 | Since it runs, ship it! (Or at least tag it for 'alpha'.) 376 | 377 | ``` 378 | $ git tag alpha_release 379 | $ git push --tags origin 380 | Total 0 (delta 0), reused 0 (delta 0) 381 | To git@github.com:jamesgraves/example-go-app.git 382 | * [new tag] alpha_release -> alpha_release 383 | ``` 384 | 385 | If we later see an update to upsilon, we can pull that to our GitHub 386 | fork, and then pull it into our project. 387 | 388 | ``` 389 | $ git subtree pull --prefix src/github.com/upstream-author/upsilon upsilon-vendor working --squash 390 | ``` 391 | You'll be offered to edit the merge commit message. 392 | 393 | Conclusion: That was waaaayyyy too much work! 394 | ============================================= 395 | 396 | OK, so if you're the one who's worried about contributing changes back 397 | to the upstream authors, there is a bit of initial effort to set up 398 | the new remotes and the commands to push and pull. 399 | 400 | And by now you're waiting for me to at least provide a fancy, smancy 401 | script that will automate all of the above. Hah! In your dreams! 402 | 403 | There is a payoff though, and a big one in my opinion. You've just 404 | saved a lot of work for the fellow developers on your team, and you've 405 | made life easy for QA and release engineering too. Here's what they 406 | do to check out the alpha release: 407 | 408 | ``` 409 | $ cd ~/ 410 | $ mkdir new_developer_workspace 411 | $ cd new_developer_workspace/ 412 | $ git clone git@github.com:jamesgraves/example-go-app.git 413 | Cloning into 'example-go-app'... 414 | remote: Counting objects: 50, done. 415 | [...] 416 | Checking connectivity... done. 417 | $ cd example-go-app/ 418 | $ export GOPATH=~/new_developer_workspace/example-go-app 419 | $ git checkout alpha_release 420 | Note: checking out 'alpha_release'. 421 | 422 | You are in 'detached HEAD' state. You can look around, make experimental 423 | changes and commit them, and you can discard any commits you make in this 424 | state without impacting any branches by performing another checkout. 425 | 426 | If you want to create a new branch to retain commits you create, you may 427 | do so (now or later) by using -b with the checkout command again. Example: 428 | 429 | git checkout -b new_branch_name 430 | 431 | HEAD is now at 6f8ced7... New functionality. 432 | 433 | ``` 434 | **That's all standard git stuff.** 435 | 436 | And now they can just run the app, continue developing, and 437 | everything, all without having to worry about the other external 438 | libraries. Or learning anything about 'git subtree' or worrying about 439 | the upstream libraries. 440 | 441 | ``` 442 | $ git remote show origin 443 | * remote origin 444 | Fetch URL: git@github.com:jamesgraves/example-go-app.git 445 | Push URL: git@github.com:jamesgraves/example-go-app.git 446 | HEAD branch: master 447 | Remote branches: 448 | master tracked 449 | working tracked 450 | Local branch configured for 'git pull': 451 | master merges with remote master 452 | Local ref configured for 'git push': 453 | master pushes to master (up to date) 454 | $ go run src/example.com/myapp/example_main.go 455 | This is main. 456 | This is Foo() from package omicron. 457 | Major new functionality for omicron. 458 | This is Bar() from package upsilon, with a small bugfix. 459 | ``` 460 | Everyone else on the team is just going to be pushing / pulling from 461 | origin, and that's that. 462 | 463 | As long as no one makes a commit that crosses library boundaries, 464 | you'll have an easy time picking out changes that can be pushed back 465 | to upstream. And you'll be able to pull in fixes for the libraries 466 | you use. 467 | 468 | QA and release engineering should be happy because your build is 100% 469 | reproducible. And they don't have to learn any new tools or 470 | procedures. Just check out a particular tag, build and Go! 471 | 472 | Final Thoughts 473 | ============== 474 | 475 | I wrote this mostly as a response to people that insist that Go must 476 | have some means of doing dependency management. I don't think Go 477 | needs to implement something like that, and other tools are better 478 | suited to the task. 479 | 480 | As always, if you see any errors or problems with this, please feel 481 | free to send me fixes. 482 | --------------------------------------------------------------------------------