| gittutorial(7) |
| ============== |
| |
| NAME |
| ---- |
| gittutorial - A tutorial introduction to Git |
| |
| SYNOPSIS |
| -------- |
| [verse] |
| git * |
| |
| DESCRIPTION |
| ----------- |
| |
| This tutorial explains how to import a new project into Git, make |
| changes to it, and share changes with other developers. |
| |
| If you are instead primarily interested in using Git to fetch a project, |
| for example, to test the latest version, you may prefer to start with |
| the first two chapters of link:user-manual.html[The Git User's Manual]. |
| |
| First, note that you can get documentation for a command such as |
| `git log --graph` with: |
| |
| ------------------------------------------------ |
| $ man git-log |
| ------------------------------------------------ |
| |
| or: |
| |
| ------------------------------------------------ |
| $ git help log |
| ------------------------------------------------ |
| |
| With the latter, you can use the manual viewer of your choice; see |
| linkgit:git-help[1] for more information. |
| |
| It is a good idea to introduce yourself to Git with your name and |
| public email address before doing any operation. The easiest |
| way to do so is: |
| |
| ------------------------------------------------ |
| $ git config --global user.name "Your Name Comes Here" |
| $ git config --global user.email you@yourdomain.example.com |
| ------------------------------------------------ |
| |
| |
| Importing a new project |
| ----------------------- |
| |
| Assume you have a tarball project.tar.gz with your initial work. You |
| can place it under Git revision control as follows. |
| |
| ------------------------------------------------ |
| $ tar xzf project.tar.gz |
| $ cd project |
| $ git init |
| ------------------------------------------------ |
| |
| Git will reply |
| |
| ------------------------------------------------ |
| Initialized empty Git repository in .git/ |
| ------------------------------------------------ |
| |
| You've now initialized the working directory--you may notice a new |
| directory created, named ".git". |
| |
| Next, tell Git to take a snapshot of the contents of all files under the |
| current directory (note the '.'), with 'git add': |
| |
| ------------------------------------------------ |
| $ git add . |
| ------------------------------------------------ |
| |
| This snapshot is now stored in a temporary staging area which Git calls |
| the "index". You can permanently store the contents of the index in the |
| repository with 'git commit': |
| |
| ------------------------------------------------ |
| $ git commit |
| ------------------------------------------------ |
| |
| This will prompt you for a commit message. You've now stored the first |
| version of your project in Git. |
| |
| Making changes |
| -------------- |
| |
| Modify some files, then add their updated contents to the index: |
| |
| ------------------------------------------------ |
| $ git add file1 file2 file3 |
| ------------------------------------------------ |
| |
| You are now ready to commit. You can see what is about to be committed |
| using 'git diff' with the --cached option: |
| |
| ------------------------------------------------ |
| $ git diff --cached |
| ------------------------------------------------ |
| |
| (Without --cached, 'git diff' will show you any changes that |
| you've made but not yet added to the index.) You can also get a brief |
| summary of the situation with 'git status': |
| |
| ------------------------------------------------ |
| $ git status |
| On branch master |
| Changes to be committed: |
| Your branch is up-to-date with 'origin/master'. |
| (use "git reset HEAD <file>..." to unstage) |
| |
| modified: file1 |
| modified: file2 |
| modified: file3 |
| |
| ------------------------------------------------ |
| |
| If you need to make any further adjustments, do so now, and then add any |
| newly modified content to the index. Finally, commit your changes with: |
| |
| ------------------------------------------------ |
| $ git commit |
| ------------------------------------------------ |
| |
| This will again prompt you for a message describing the change, and then |
| record a new version of the project. |
| |
| Alternatively, instead of running 'git add' beforehand, you can use |
| |
| ------------------------------------------------ |
| $ git commit -a |
| ------------------------------------------------ |
| |
| which will automatically notice any modified (but not new) files, add |
| them to the index, and commit, all in one step. |
| |
| A note on commit messages: Though not required, it's a good idea to |
| begin the commit message with a single short (less than 50 character) |
| line summarizing the change, followed by a blank line and then a more |
| thorough description. The text up to the first blank line in a commit |
| message is treated as the commit title, and that title is used |
| throughout Git. For example, linkgit:git-format-patch[1] turns a |
| commit into email, and it uses the title on the Subject line and the |
| rest of the commit in the body. |
| |
| Git tracks content not files |
| ---------------------------- |
| |
| Many revision control systems provide an `add` command that tells the |
| system to start tracking changes to a new file. Git's `add` command |
| does something simpler and more powerful: 'git add' is used both for new |
| and newly modified files, and in both cases it takes a snapshot of the |
| given files and stages that content in the index, ready for inclusion in |
| the next commit. |
| |
| Viewing project history |
| ----------------------- |
| |
| At any point you can view the history of your changes using |
| |
| ------------------------------------------------ |
| $ git log |
| ------------------------------------------------ |
| |
| If you also want to see complete diffs at each step, use |
| |
| ------------------------------------------------ |
| $ git log -p |
| ------------------------------------------------ |
| |
| Often the overview of the change is useful to get a feel of |
| each step |
| |
| ------------------------------------------------ |
| $ git log --stat --summary |
| ------------------------------------------------ |
| |
| Managing branches |
| ----------------- |
| |
| A single Git repository can maintain multiple branches of |
| development. To create a new branch named "experimental", use |
| |
| ------------------------------------------------ |
| $ git branch experimental |
| ------------------------------------------------ |
| |
| If you now run |
| |
| ------------------------------------------------ |
| $ git branch |
| ------------------------------------------------ |
| |
| you'll get a list of all existing branches: |
| |
| ------------------------------------------------ |
| experimental |
| * master |
| ------------------------------------------------ |
| |
| The "experimental" branch is the one you just created, and the |
| "master" branch is a default branch that was created for you |
| automatically. The asterisk marks the branch you are currently on; |
| type |
| |
| ------------------------------------------------ |
| $ git checkout experimental |
| ------------------------------------------------ |
| |
| to switch to the experimental branch. Now edit a file, commit the |
| change, and switch back to the master branch: |
| |
| ------------------------------------------------ |
| (edit file) |
| $ git commit -a |
| $ git checkout master |
| ------------------------------------------------ |
| |
| Check that the change you made is no longer visible, since it was |
| made on the experimental branch and you're back on the master branch. |
| |
| You can make a different change on the master branch: |
| |
| ------------------------------------------------ |
| (edit file) |
| $ git commit -a |
| ------------------------------------------------ |
| |
| at this point the two branches have diverged, with different changes |
| made in each. To merge the changes made in experimental into master, run |
| |
| ------------------------------------------------ |
| $ git merge experimental |
| ------------------------------------------------ |
| |
| If the changes don't conflict, you're done. If there are conflicts, |
| markers will be left in the problematic files showing the conflict; |
| |
| ------------------------------------------------ |
| $ git diff |
| ------------------------------------------------ |
| |
| will show this. Once you've edited the files to resolve the |
| conflicts, |
| |
| ------------------------------------------------ |
| $ git commit -a |
| ------------------------------------------------ |
| |
| will commit the result of the merge. Finally, |
| |
| ------------------------------------------------ |
| $ gitk |
| ------------------------------------------------ |
| |
| will show a nice graphical representation of the resulting history. |
| |
| At this point you could delete the experimental branch with |
| |
| ------------------------------------------------ |
| $ git branch -d experimental |
| ------------------------------------------------ |
| |
| This command ensures that the changes in the experimental branch are |
| already in the current branch. |
| |
| If you develop on a branch crazy-idea, then regret it, you can always |
| delete the branch with |
| |
| ------------------------------------- |
| $ git branch -D crazy-idea |
| ------------------------------------- |
| |
| Branches are cheap and easy, so this is a good way to try something |
| out. |
| |
| Using Git for collaboration |
| --------------------------- |
| |
| Suppose that Alice has started a new project with a Git repository in |
| /home/alice/project, and that Bob, who has a home directory on the |
| same machine, wants to contribute. |
| |
| Bob begins with: |
| |
| ------------------------------------------------ |
| bob$ git clone /home/alice/project myrepo |
| ------------------------------------------------ |
| |
| This creates a new directory "myrepo" containing a clone of Alice's |
| repository. The clone is on an equal footing with the original |
| project, possessing its own copy of the original project's history. |
| |
| Bob then makes some changes and commits them: |
| |
| ------------------------------------------------ |
| (edit files) |
| bob$ git commit -a |
| (repeat as necessary) |
| ------------------------------------------------ |
| |
| When he's ready, he tells Alice to pull changes from the repository |
| at /home/bob/myrepo. She does this with: |
| |
| ------------------------------------------------ |
| alice$ cd /home/alice/project |
| alice$ git pull /home/bob/myrepo master |
| ------------------------------------------------ |
| |
| This merges the changes from Bob's "master" branch into Alice's |
| current branch. If Alice has made her own changes in the meantime, |
| then she may need to manually fix any conflicts. |
| |
| The "pull" command thus performs two operations: it fetches changes |
| from a remote branch, then merges them into the current branch. |
| |
| Note that in general, Alice would want her local changes committed before |
| initiating this "pull". If Bob's work conflicts with what Alice did since |
| their histories forked, Alice will use her working tree and the index to |
| resolve conflicts, and existing local changes will interfere with the |
| conflict resolution process (Git will still perform the fetch but will |
| refuse to merge --- Alice will have to get rid of her local changes in |
| some way and pull again when this happens). |
| |
| Alice can peek at what Bob did without merging first, using the "fetch" |
| command; this allows Alice to inspect what Bob did, using a special |
| symbol "FETCH_HEAD", in order to determine if he has anything worth |
| pulling, like this: |
| |
| ------------------------------------------------ |
| alice$ git fetch /home/bob/myrepo master |
| alice$ git log -p HEAD..FETCH_HEAD |
| ------------------------------------------------ |
| |
| This operation is safe even if Alice has uncommitted local changes. |
| The range notation "HEAD..FETCH_HEAD" means "show everything that is reachable |
| from the FETCH_HEAD but exclude anything that is reachable from HEAD". |
| Alice already knows everything that leads to her current state (HEAD), |
| and reviews what Bob has in his state (FETCH_HEAD) that she has not |
| seen with this command. |
| |
| If Alice wants to visualize what Bob did since their histories forked |
| she can issue the following command: |
| |
| ------------------------------------------------ |
| $ gitk HEAD..FETCH_HEAD |
| ------------------------------------------------ |
| |
| This uses the same two-dot range notation we saw earlier with 'git log'. |
| |
| Alice may want to view what both of them did since they forked. |
| She can use three-dot form instead of the two-dot form: |
| |
| ------------------------------------------------ |
| $ gitk HEAD...FETCH_HEAD |
| ------------------------------------------------ |
| |
| This means "show everything that is reachable from either one, but |
| exclude anything that is reachable from both of them". |
| |
| Please note that these range notation can be used with both gitk |
| and "git log". |
| |
| After inspecting what Bob did, if there is nothing urgent, Alice may |
| decide to continue working without pulling from Bob. If Bob's history |
| does have something Alice would immediately need, Alice may choose to |
| stash her work-in-progress first, do a "pull", and then finally unstash |
| her work-in-progress on top of the resulting history. |
| |
| When you are working in a small closely knit group, it is not |
| unusual to interact with the same repository over and over |
| again. By defining 'remote' repository shorthand, you can make |
| it easier: |
| |
| ------------------------------------------------ |
| alice$ git remote add bob /home/bob/myrepo |
| ------------------------------------------------ |
| |
| With this, Alice can perform the first part of the "pull" operation |
| alone using the 'git fetch' command without merging them with her own |
| branch, using: |
| |
| ------------------------------------- |
| alice$ git fetch bob |
| ------------------------------------- |
| |
| Unlike the longhand form, when Alice fetches from Bob using a |
| remote repository shorthand set up with 'git remote', what was |
| fetched is stored in a remote-tracking branch, in this case |
| `bob/master`. So after this: |
| |
| ------------------------------------- |
| alice$ git log -p master..bob/master |
| ------------------------------------- |
| |
| shows a list of all the changes that Bob made since he branched from |
| Alice's master branch. |
| |
| After examining those changes, Alice |
| could merge the changes into her master branch: |
| |
| ------------------------------------- |
| alice$ git merge bob/master |
| ------------------------------------- |
| |
| This `merge` can also be done by 'pulling from her own remote-tracking |
| branch', like this: |
| |
| ------------------------------------- |
| alice$ git pull . remotes/bob/master |
| ------------------------------------- |
| |
| Note that git pull always merges into the current branch, |
| regardless of what else is given on the command line. |
| |
| Later, Bob can update his repo with Alice's latest changes using |
| |
| ------------------------------------- |
| bob$ git pull |
| ------------------------------------- |
| |
| Note that he doesn't need to give the path to Alice's repository; |
| when Bob cloned Alice's repository, Git stored the location of her |
| repository in the repository configuration, and that location is |
| used for pulls: |
| |
| ------------------------------------- |
| bob$ git config --get remote.origin.url |
| /home/alice/project |
| ------------------------------------- |
| |
| (The complete configuration created by 'git clone' is visible using |
| `git config -l`, and the linkgit:git-config[1] man page |
| explains the meaning of each option.) |
| |
| Git also keeps a pristine copy of Alice's master branch under the |
| name "origin/master": |
| |
| ------------------------------------- |
| bob$ git branch -r |
| origin/master |
| ------------------------------------- |
| |
| If Bob later decides to work from a different host, he can still |
| perform clones and pulls using the ssh protocol: |
| |
| ------------------------------------- |
| bob$ git clone alice.org:/home/alice/project myrepo |
| ------------------------------------- |
| |
| Alternatively, Git has a native protocol, or can use http; |
| see linkgit:git-pull[1] for details. |
| |
| Git can also be used in a CVS-like mode, with a central repository |
| that various users push changes to; see linkgit:git-push[1] and |
| linkgit:gitcvs-migration[7]. |
| |
| Exploring history |
| ----------------- |
| |
| Git history is represented as a series of interrelated commits. We |
| have already seen that the 'git log' command can list those commits. |
| Note that first line of each git log entry also gives a name for the |
| commit: |
| |
| ------------------------------------- |
| $ git log |
| commit c82a22c39cbc32576f64f5c6b3f24b99ea8149c7 |
| Author: Junio C Hamano <junkio@cox.net> |
| Date: Tue May 16 17:18:22 2006 -0700 |
| |
| merge-base: Clarify the comments on post processing. |
| ------------------------------------- |
| |
| We can give this name to 'git show' to see the details about this |
| commit. |
| |
| ------------------------------------- |
| $ git show c82a22c39cbc32576f64f5c6b3f24b99ea8149c7 |
| ------------------------------------- |
| |
| But there are other ways to refer to commits. You can use any initial |
| part of the name that is long enough to uniquely identify the commit: |
| |
| ------------------------------------- |
| $ git show c82a22c39c # the first few characters of the name are |
| # usually enough |
| $ git show HEAD # the tip of the current branch |
| $ git show experimental # the tip of the "experimental" branch |
| ------------------------------------- |
| |
| Every commit usually has one "parent" commit |
| which points to the previous state of the project: |
| |
| ------------------------------------- |
| $ git show HEAD^ # to see the parent of HEAD |
| $ git show HEAD^^ # to see the grandparent of HEAD |
| $ git show HEAD~4 # to see the great-great grandparent of HEAD |
| ------------------------------------- |
| |
| Note that merge commits may have more than one parent: |
| |
| ------------------------------------- |
| $ git show HEAD^1 # show the first parent of HEAD (same as HEAD^) |
| $ git show HEAD^2 # show the second parent of HEAD |
| ------------------------------------- |
| |
| You can also give commits names of your own; after running |
| |
| ------------------------------------- |
| $ git tag v2.5 1b2e1d63ff |
| ------------------------------------- |
| |
| you can refer to 1b2e1d63ff by the name "v2.5". If you intend to |
| share this name with other people (for example, to identify a release |
| version), you should create a "tag" object, and perhaps sign it; see |
| linkgit:git-tag[1] for details. |
| |
| Any Git command that needs to know a commit can take any of these |
| names. For example: |
| |
| ------------------------------------- |
| $ git diff v2.5 HEAD # compare the current HEAD to v2.5 |
| $ git branch stable v2.5 # start a new branch named "stable" based |
| # at v2.5 |
| $ git reset --hard HEAD^ # reset your current branch and working |
| # directory to its state at HEAD^ |
| ------------------------------------- |
| |
| Be careful with that last command: in addition to losing any changes |
| in the working directory, it will also remove all later commits from |
| this branch. If this branch is the only branch containing those |
| commits, they will be lost. Also, don't use 'git reset' on a |
| publicly-visible branch that other developers pull from, as it will |
| force needless merges on other developers to clean up the history. |
| If you need to undo changes that you have pushed, use 'git revert' |
| instead. |
| |
| The 'git grep' command can search for strings in any version of your |
| project, so |
| |
| ------------------------------------- |
| $ git grep "hello" v2.5 |
| ------------------------------------- |
| |
| searches for all occurrences of "hello" in v2.5. |
| |
| If you leave out the commit name, 'git grep' will search any of the |
| files it manages in your current directory. So |
| |
| ------------------------------------- |
| $ git grep "hello" |
| ------------------------------------- |
| |
| is a quick way to search just the files that are tracked by Git. |
| |
| Many Git commands also take sets of commits, which can be specified |
| in a number of ways. Here are some examples with 'git log': |
| |
| ------------------------------------- |
| $ git log v2.5..v2.6 # commits between v2.5 and v2.6 |
| $ git log v2.5.. # commits since v2.5 |
| $ git log --since="2 weeks ago" # commits from the last 2 weeks |
| $ git log v2.5.. Makefile # commits since v2.5 which modify |
| # Makefile |
| ------------------------------------- |
| |
| You can also give 'git log' a "range" of commits where the first is not |
| necessarily an ancestor of the second; for example, if the tips of |
| the branches "stable" and "master" diverged from a common |
| commit some time ago, then |
| |
| ------------------------------------- |
| $ git log stable..master |
| ------------------------------------- |
| |
| will list commits made in the master branch but not in the |
| stable branch, while |
| |
| ------------------------------------- |
| $ git log master..stable |
| ------------------------------------- |
| |
| will show the list of commits made on the stable branch but not |
| the master branch. |
| |
| The 'git log' command has a weakness: it must present commits in a |
| list. When the history has lines of development that diverged and |
| then merged back together, the order in which 'git log' presents |
| those commits is meaningless. |
| |
| Most projects with multiple contributors (such as the Linux kernel, |
| or Git itself) have frequent merges, and 'gitk' does a better job of |
| visualizing their history. For example, |
| |
| ------------------------------------- |
| $ gitk --since="2 weeks ago" drivers/ |
| ------------------------------------- |
| |
| allows you to browse any commits from the last 2 weeks of commits |
| that modified files under the "drivers" directory. (Note: you can |
| adjust gitk's fonts by holding down the control key while pressing |
| "-" or "+".) |
| |
| Finally, most commands that take filenames will optionally allow you |
| to precede any filename by a commit, to specify a particular version |
| of the file: |
| |
| ------------------------------------- |
| $ git diff v2.5:Makefile HEAD:Makefile.in |
| ------------------------------------- |
| |
| You can also use 'git show' to see any such file: |
| |
| ------------------------------------- |
| $ git show v2.5:Makefile |
| ------------------------------------- |
| |
| Next Steps |
| ---------- |
| |
| This tutorial should be enough to perform basic distributed revision |
| control for your projects. However, to fully understand the depth |
| and power of Git you need to understand two simple ideas on which it |
| is based: |
| |
| * The object database is the rather elegant system used to |
| store the history of your project--files, directories, and |
| commits. |
| |
| * The index file is a cache of the state of a directory tree, |
| used to create commits, check out working directories, and |
| hold the various trees involved in a merge. |
| |
| Part two of this tutorial explains the object |
| database, the index file, and a few other odds and ends that you'll |
| need to make the most of Git. You can find it at linkgit:gittutorial-2[7]. |
| |
| If you don't want to continue with that right away, a few other |
| digressions that may be interesting at this point are: |
| |
| * linkgit:git-format-patch[1], linkgit:git-am[1]: These convert |
| series of git commits into emailed patches, and vice versa, |
| useful for projects such as the Linux kernel which rely heavily |
| on emailed patches. |
| |
| * linkgit:git-bisect[1]: When there is a regression in your |
| project, one way to track down the bug is by searching through |
| the history to find the exact commit that's to blame. Git bisect |
| can help you perform a binary search for that commit. It is |
| smart enough to perform a close-to-optimal search even in the |
| case of complex non-linear history with lots of merged branches. |
| |
| * linkgit:gitworkflows[7]: Gives an overview of recommended |
| workflows. |
| |
| * linkgit:giteveryday[7]: Everyday Git with 20 Commands Or So. |
| |
| * linkgit:gitcvs-migration[7]: Git for CVS users. |
| |
| SEE ALSO |
| -------- |
| linkgit:gittutorial-2[7], |
| linkgit:gitcvs-migration[7], |
| linkgit:gitcore-tutorial[7], |
| linkgit:gitglossary[7], |
| linkgit:git-help[1], |
| linkgit:gitworkflows[7], |
| linkgit:giteveryday[7], |
| link:user-manual.html[The Git User's Manual] |
| |
| GIT |
| --- |
| Part of the linkgit:git[1] suite. |