gittutorial(7) Manual Page

NAME

   gittutorial - A tutorial introduction to Git

SYNOPSIS

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 [1]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 [2]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:
  (use "git restore --staged ..". 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 (no more than 50 characters) 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, [3]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 switch 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 switch 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 [4]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 [5]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 [6]git-push(1) and [7]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 
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 [8]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
   [9]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:
     * [10]git-format-patch(1), [11]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.
     * [12]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.
     * [13]gitworkflows(7): Gives an overview of recommended workflows.
     * [14]giteveryday(7): Everyday Git with 20 Commands Or So.
     * [15]gitcvs-migration(7): Git for CVS users.

SEE ALSO

   [16]gittutorial-2(7), [17]gitcvs-migration(7), [18]gitcore-tutorial(7),
   [19]gitglossary(7), [20]git-help(1), [21]gitworkflows(7), [22]giteveryday(7),
   [23]The Git User's Manual

GIT

   Part of the [24]git(1) suite
     ____________________________________________________________________________

   Last updated 2023-10-18 13:44:22 PDT

References

   1. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/user-manual.html
   2. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/git-help.html
   3. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/git-format-patch.html
   4. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/git-config.html
   5. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/git-pull.html
   6. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/git-push.html
   7. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/gitcvs-migration.html
   8. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/git-tag.html
   9. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/gittutorial-2.html
  10. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/git-format-patch.html
  11. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/git-am.html
  12. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/git-bisect.html
  13. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/gitworkflows.html
  14. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/giteveryday.html
  15. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/gitcvs-migration.html
  16. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/gittutorial-2.html
  17. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/gitcvs-migration.html
  18. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/gitcore-tutorial.html
  19. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/gitglossary.html
  20. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/git-help.html
  21. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/gitworkflows.html
  22. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/giteveryday.html
  23. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/user-manual.html
  24. https://mirrors.edge.kernel.org/pub/software/scm/git/docs/git.html