1gittutorial(7) 2============== 3 4NAME 5---- 6gittutorial - A tutorial introduction to git (for version 1.5.1 or newer) 7 8SYNOPSIS 9-------- 10git * 11 12DESCRIPTION 13----------- 14 15This tutorial explains how to import a new project into git, make 16changes to it, and share changes with other developers. 17 18If you are instead primarily interested in using git to fetch a project, 19for example, to test the latest version, you may prefer to start with 20the first two chapters of link:user-manual.html[The Git User's Manual]. 21 22First, note that you can get documentation for a command such as "git 23diff" with: 24 25------------------------------------------------ 26$ man git-diff 27------------------------------------------------ 28 29It is a good idea to introduce yourself to git with your name and 30public email address before doing any operation. The easiest 31way to do so is: 32 33------------------------------------------------ 34$ git config --global user.name "Your Name Comes Here" 35$ git config --global user.email you@yourdomain.example.com 36------------------------------------------------ 37 38 39Importing a new project 40----------------------- 41 42Assume you have a tarball project.tar.gz with your initial work. You 43can place it under git revision control as follows. 44 45------------------------------------------------ 46$ tar xzf project.tar.gz 47$ cd project 48$ git init 49------------------------------------------------ 50 51Git will reply 52 53------------------------------------------------ 54Initialized empty Git repository in .git/ 55------------------------------------------------ 56 57You've now initialized the working directory--you may notice a new 58directory created, named ".git". 59 60Next, tell git to take a snapshot of the contents of all files under the 61current directory (note the '.'), with linkgit:git-add[1]: 62 63------------------------------------------------ 64$ git add . 65------------------------------------------------ 66 67This snapshot is now stored in a temporary staging area which git calls 68the "index". You can permanently store the contents of the index in the 69repository with linkgit:git-commit[1]: 70 71------------------------------------------------ 72$ git commit 73------------------------------------------------ 74 75This will prompt you for a commit message. You've now stored the first 76version of your project in git. 77 78Making changes 79-------------- 80 81Modify some files, then add their updated contents to the index: 82 83------------------------------------------------ 84$ git add file1 file2 file3 85------------------------------------------------ 86 87You are now ready to commit. You can see what is about to be committed 88using linkgit:git-diff[1] with the --cached option: 89 90------------------------------------------------ 91$ git diff --cached 92------------------------------------------------ 93 94(Without --cached, linkgit:git-diff[1] will show you any changes that 95you've made but not yet added to the index.) You can also get a brief 96summary of the situation with linkgit:git-status[1]: 97 98------------------------------------------------ 99$ git status 100# On branch master 101# Changes to be committed: 102# (use "git reset HEAD <file>..." to unstage) 103# 104# modified: file1 105# modified: file2 106# modified: file3 107# 108------------------------------------------------ 109 110If you need to make any further adjustments, do so now, and then add any 111newly modified content to the index. Finally, commit your changes with: 112 113------------------------------------------------ 114$ git commit 115------------------------------------------------ 116 117This will again prompt your for a message describing the change, and then 118record a new version of the project. 119 120Alternatively, instead of running `git add` beforehand, you can use 121 122------------------------------------------------ 123$ git commit -a 124------------------------------------------------ 125 126which will automatically notice any modified (but not new) files, add 127them to the index, and commit, all in one step. 128 129A note on commit messages: Though not required, it's a good idea to 130begin the commit message with a single short (less than 50 character) 131line summarizing the change, followed by a blank line and then a more 132thorough description. Tools that turn commits into email, for 133example, use the first line on the Subject: line and the rest of the 134commit in the body. 135 136Git tracks content not files 137---------------------------- 138 139Many revision control systems provide an "add" command that tells the 140system to start tracking changes to a new file. Git's "add" command 141does something simpler and more powerful: `git add` is used both for new 142and newly modified files, and in both cases it takes a snapshot of the 143given files and stages that content in the index, ready for inclusion in 144the next commit. 145 146Viewing project history 147----------------------- 148 149At any point you can view the history of your changes using 150 151------------------------------------------------ 152$ git log 153------------------------------------------------ 154 155If you also want to see complete diffs at each step, use 156 157------------------------------------------------ 158$ git log -p 159------------------------------------------------ 160 161Often the overview of the change is useful to get a feel of 162each step 163 164------------------------------------------------ 165$ git log --stat --summary 166------------------------------------------------ 167 168Managing branches 169----------------- 170 171A single git repository can maintain multiple branches of 172development. To create a new branch named "experimental", use 173 174------------------------------------------------ 175$ git branch experimental 176------------------------------------------------ 177 178If you now run 179 180------------------------------------------------ 181$ git branch 182------------------------------------------------ 183 184you'll get a list of all existing branches: 185 186------------------------------------------------ 187 experimental 188* master 189------------------------------------------------ 190 191The "experimental" branch is the one you just created, and the 192"master" branch is a default branch that was created for you 193automatically. The asterisk marks the branch you are currently on; 194type 195 196------------------------------------------------ 197$ git checkout experimental 198------------------------------------------------ 199 200to switch to the experimental branch. Now edit a file, commit the 201change, and switch back to the master branch: 202 203------------------------------------------------ 204(edit file) 205$ git commit -a 206$ git checkout master 207------------------------------------------------ 208 209Check that the change you made is no longer visible, since it was 210made on the experimental branch and you're back on the master branch. 211 212You can make a different change on the master branch: 213 214------------------------------------------------ 215(edit file) 216$ git commit -a 217------------------------------------------------ 218 219at this point the two branches have diverged, with different changes 220made in each. To merge the changes made in experimental into master, run 221 222------------------------------------------------ 223$ git merge experimental 224------------------------------------------------ 225 226If the changes don't conflict, you're done. If there are conflicts, 227markers will be left in the problematic files showing the conflict; 228 229------------------------------------------------ 230$ git diff 231------------------------------------------------ 232 233will show this. Once you've edited the files to resolve the 234conflicts, 235 236------------------------------------------------ 237$ git commit -a 238------------------------------------------------ 239 240will commit the result of the merge. Finally, 241 242------------------------------------------------ 243$ gitk 244------------------------------------------------ 245 246will show a nice graphical representation of the resulting history. 247 248At this point you could delete the experimental branch with 249 250------------------------------------------------ 251$ git branch -d experimental 252------------------------------------------------ 253 254This command ensures that the changes in the experimental branch are 255already in the current branch. 256 257If you develop on a branch crazy-idea, then regret it, you can always 258delete the branch with 259 260------------------------------------- 261$ git branch -D crazy-idea 262------------------------------------- 263 264Branches are cheap and easy, so this is a good way to try something 265out. 266 267Using git for collaboration 268--------------------------- 269 270Suppose that Alice has started a new project with a git repository in 271/home/alice/project, and that Bob, who has a home directory on the 272same machine, wants to contribute. 273 274Bob begins with: 275 276------------------------------------------------ 277$ git clone /home/alice/project myrepo 278------------------------------------------------ 279 280This creates a new directory "myrepo" containing a clone of Alice's 281repository. The clone is on an equal footing with the original 282project, possessing its own copy of the original project's history. 283 284Bob then makes some changes and commits them: 285 286------------------------------------------------ 287(edit files) 288$ git commit -a 289(repeat as necessary) 290------------------------------------------------ 291 292When he's ready, he tells Alice to pull changes from the repository 293at /home/bob/myrepo. She does this with: 294 295------------------------------------------------ 296$ cd /home/alice/project 297$ git pull /home/bob/myrepo master 298------------------------------------------------ 299 300This merges the changes from Bob's "master" branch into Alice's 301current branch. If Alice has made her own changes in the meantime, 302then she may need to manually fix any conflicts. (Note that the 303"master" argument in the above command is actually unnecessary, as it 304is the default.) 305 306The "pull" command thus performs two operations: it fetches changes 307from a remote branch, then merges them into the current branch. 308 309When you are working in a small closely knit group, it is not 310unusual to interact with the same repository over and over 311again. By defining 'remote' repository shorthand, you can make 312it easier: 313 314------------------------------------------------ 315$ git remote add bob /home/bob/myrepo 316------------------------------------------------ 317 318With this, Alice can perform the first operation alone using the 319"git fetch" command without merging them with her own branch, 320using: 321 322------------------------------------- 323$ git fetch bob 324------------------------------------- 325 326Unlike the longhand form, when Alice fetches from Bob using a 327remote repository shorthand set up with `git remote`, what was 328fetched is stored in a remote tracking branch, in this case 329`bob/master`. So after this: 330 331------------------------------------- 332$ git log -p master..bob/master 333------------------------------------- 334 335shows a list of all the changes that Bob made since he branched from 336Alice's master branch. 337 338After examining those changes, Alice 339could merge the changes into her master branch: 340 341------------------------------------- 342$ git merge bob/master 343------------------------------------- 344 345This `merge` can also be done by 'pulling from her own remote 346tracking branch', like this: 347 348------------------------------------- 349$ git pull . remotes/bob/master 350------------------------------------- 351 352Note that git pull always merges into the current branch, 353regardless of what else is given on the command line. 354 355Later, Bob can update his repo with Alice's latest changes using 356 357------------------------------------- 358$ git pull 359------------------------------------- 360 361Note that he doesn't need to give the path to Alice's repository; 362when Bob cloned Alice's repository, git stored the location of her 363repository in the repository configuration, and that location is 364used for pulls: 365 366------------------------------------- 367$ git config --get remote.origin.url 368/home/alice/project 369------------------------------------- 370 371(The complete configuration created by git-clone is visible using 372"git config -l", and the linkgit:git-config[1] man page 373explains the meaning of each option.) 374 375Git also keeps a pristine copy of Alice's master branch under the 376name "origin/master": 377 378------------------------------------- 379$ git branch -r 380 origin/master 381------------------------------------- 382 383If Bob later decides to work from a different host, he can still 384perform clones and pulls using the ssh protocol: 385 386------------------------------------- 387$ git clone alice.org:/home/alice/project myrepo 388------------------------------------- 389 390Alternatively, git has a native protocol, or can use rsync or http; 391see linkgit:git-pull[1] for details. 392 393Git can also be used in a CVS-like mode, with a central repository 394that various users push changes to; see linkgit:git-push[1] and 395linkgit:gitcvs-migration[7][git for CVS users]. 396 397Exploring history 398----------------- 399 400Git history is represented as a series of interrelated commits. We 401have already seen that the git log command can list those commits. 402Note that first line of each git log entry also gives a name for the 403commit: 404 405------------------------------------- 406$ git log 407commit c82a22c39cbc32576f64f5c6b3f24b99ea8149c7 408Author: Junio C Hamano <junkio@cox.net> 409Date: Tue May 16 17:18:22 2006 -0700 410 411 merge-base: Clarify the comments on post processing. 412------------------------------------- 413 414We can give this name to git show to see the details about this 415commit. 416 417------------------------------------- 418$ git show c82a22c39cbc32576f64f5c6b3f24b99ea8149c7 419------------------------------------- 420 421But there are other ways to refer to commits. You can use any initial 422part of the name that is long enough to uniquely identify the commit: 423 424------------------------------------- 425$ git show c82a22c39c # the first few characters of the name are 426 # usually enough 427$ git show HEAD # the tip of the current branch 428$ git show experimental # the tip of the "experimental" branch 429------------------------------------- 430 431Every commit usually has one "parent" commit 432which points to the previous state of the project: 433 434------------------------------------- 435$ git show HEAD^ # to see the parent of HEAD 436$ git show HEAD^^ # to see the grandparent of HEAD 437$ git show HEAD~4 # to see the great-great grandparent of HEAD 438------------------------------------- 439 440Note that merge commits may have more than one parent: 441 442------------------------------------- 443$ git show HEAD^1 # show the first parent of HEAD (same as HEAD^) 444$ git show HEAD^2 # show the second parent of HEAD 445------------------------------------- 446 447You can also give commits names of your own; after running 448 449------------------------------------- 450$ git-tag v2.5 1b2e1d63ff 451------------------------------------- 452 453you can refer to 1b2e1d63ff by the name "v2.5". If you intend to 454share this name with other people (for example, to identify a release 455version), you should create a "tag" object, and perhaps sign it; see 456linkgit:git-tag[1] for details. 457 458Any git command that needs to know a commit can take any of these 459names. For example: 460 461------------------------------------- 462$ git diff v2.5 HEAD # compare the current HEAD to v2.5 463$ git branch stable v2.5 # start a new branch named "stable" based 464 # at v2.5 465$ git reset --hard HEAD^ # reset your current branch and working 466 # directory to its state at HEAD^ 467------------------------------------- 468 469Be careful with that last command: in addition to losing any changes 470in the working directory, it will also remove all later commits from 471this branch. If this branch is the only branch containing those 472commits, they will be lost. Also, don't use "git reset" on a 473publicly-visible branch that other developers pull from, as it will 474force needless merges on other developers to clean up the history. 475If you need to undo changes that you have pushed, use linkgit:git-revert[1] 476instead. 477 478The git grep command can search for strings in any version of your 479project, so 480 481------------------------------------- 482$ git grep "hello" v2.5 483------------------------------------- 484 485searches for all occurrences of "hello" in v2.5. 486 487If you leave out the commit name, git grep will search any of the 488files it manages in your current directory. So 489 490------------------------------------- 491$ git grep "hello" 492------------------------------------- 493 494is a quick way to search just the files that are tracked by git. 495 496Many git commands also take sets of commits, which can be specified 497in a number of ways. Here are some examples with git log: 498 499------------------------------------- 500$ git log v2.5..v2.6 # commits between v2.5 and v2.6 501$ git log v2.5.. # commits since v2.5 502$ git log --since="2 weeks ago" # commits from the last 2 weeks 503$ git log v2.5.. Makefile # commits since v2.5 which modify 504 # Makefile 505------------------------------------- 506 507You can also give git log a "range" of commits where the first is not 508necessarily an ancestor of the second; for example, if the tips of 509the branches "stable-release" and "master" diverged from a common 510commit some time ago, then 511 512------------------------------------- 513$ git log stable..experimental 514------------------------------------- 515 516will list commits made in the experimental branch but not in the 517stable branch, while 518 519------------------------------------- 520$ git log experimental..stable 521------------------------------------- 522 523will show the list of commits made on the stable branch but not 524the experimental branch. 525 526The "git log" command has a weakness: it must present commits in a 527list. When the history has lines of development that diverged and 528then merged back together, the order in which "git log" presents 529those commits is meaningless. 530 531Most projects with multiple contributors (such as the linux kernel, 532or git itself) have frequent merges, and gitk does a better job of 533visualizing their history. For example, 534 535------------------------------------- 536$ gitk --since="2 weeks ago" drivers/ 537------------------------------------- 538 539allows you to browse any commits from the last 2 weeks of commits 540that modified files under the "drivers" directory. (Note: you can 541adjust gitk's fonts by holding down the control key while pressing 542"-" or "+".) 543 544Finally, most commands that take filenames will optionally allow you 545to precede any filename by a commit, to specify a particular version 546of the file: 547 548------------------------------------- 549$ git diff v2.5:Makefile HEAD:Makefile.in 550------------------------------------- 551 552You can also use "git show" to see any such file: 553 554------------------------------------- 555$ git show v2.5:Makefile 556------------------------------------- 557 558Next Steps 559---------- 560 561This tutorial should be enough to perform basic distributed revision 562control for your projects. However, to fully understand the depth 563and power of git you need to understand two simple ideas on which it 564is based: 565 566 * The object database is the rather elegant system used to 567 store the history of your project--files, directories, and 568 commits. 569 570 * The index file is a cache of the state of a directory tree, 571 used to create commits, check out working directories, and 572 hold the various trees involved in a merge. 573 574linkgit:gittutorial-2[7][Part two of this tutorial] explains the object 575database, the index file, and a few other odds and ends that you'll 576need to make the most of git. 577 578If you don't want to continue with that right away, a few other 579digressions that may be interesting at this point are: 580 581 * linkgit:git-format-patch[1], linkgit:git-am[1]: These convert 582 series of git commits into emailed patches, and vice versa, 583 useful for projects such as the linux kernel which rely heavily 584 on emailed patches. 585 586 * linkgit:git-bisect[1]: When there is a regression in your 587 project, one way to track down the bug is by searching through 588 the history to find the exact commit that's to blame. Git bisect 589 can help you perform a binary search for that commit. It is 590 smart enough to perform a close-to-optimal search even in the 591 case of complex non-linear history with lots of merged branches. 592 593 * link:everyday.html[Everyday GIT with 20 Commands Or So] 594 595 * linkgit:gitcvs-migration[7][git for CVS users]. 596 597SEE ALSO 598-------- 599linkgit:gittutorial-2[7], 600linkgit:gitcvs-migration[7], 601linkgit:gitcore-tutorial[7], 602linkgit:gitglossary[7], 603link:everyday.html[Everyday git], 604link:user-manual.html[The Git User's Manual] 605 606GIT 607--- 608Part of the linkgit:git[7] suite.