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Version 2.43.0 ▼ gittutorial last updated in 2.43.0
Changes in the gittutorial manual
1.2.43.0
2.2.42.0
3.2.41.0 ■|
4. 2.33.1
5. 2.33.0
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Check your version of git by running
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—
gittutorial - A tutorial introduction to Git
SYNOPSIS
DESCRIPTION
This tutorial explains how to import a new project into Git, make changes to it, and share changes with other
developers.
Git - gittutorial Documentation
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 The Git User's Manual.
First, note that you can get documentation for a command such as git log -- graph with:
$ man git-log
$ git help log
With the latter, you can use the manual viewer of your choice; see git-help[1] for more information.
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Git - gittutorial Documentation
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 filel 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: filel
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:
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$ 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, 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
Git - gittutorial Documentation
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
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Git - gittutorial Documentation
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:
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bob$ git clone /home/alice/project my repo
Git - gittutorial Documentation
This creates a new directory my repo 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
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