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       gittutorial - A tutorial	introduction to	Git

       git *

       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 The	Git User's Manual[1].

       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.

       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 "Your Name Comes Here"
	   $ git config	--global

       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.

       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 restore --staged	<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

	   $ 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, 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.

       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.

       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

       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:

	   * 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,

	   $ 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

       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

       (The complete configuration created by git clone	is visible using git
       config -l, and the git-config(1)	man page explains the meaning of each

       Git also	keeps a	pristine copy of Alice's master	branch under the name

	   bob$	git branch -r

       If Bob later decides to work from a different host, he can still
       perform clones and pulls	using the ssh protocol:

	   bob$	git clone	myrepo

       Alternatively, Git has a	native protocol, or can	use http; see 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 git-push(1) and gitcvs-migration(7).

       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
       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

       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

       You can also use	git show to see	any such file:

	   $ git show v2.5:Makefile

       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

       o   The object database is the rather elegant system used to store the
	   history of your project--files, directories,	and commits.

       o   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 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:

       o   git-format-patch(1),	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.

       o   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.

       o   gitworkflows(7): Gives an overview of recommended workflows.

       o   giteveryday(7): Everyday Git	with 20	Commands Or So.

       o   gitcvs-migration(7):	Git for	CVS users.

       gittutorial-2(7), gitcvs-migration(7), gitcore-tutorial(7),
       gitglossary(7), git-help(1), gitworkflows(7), giteveryday(7), The Git
       User's Manual[1]

       Part of the git(1) suite

	1. The Git User's Manual

Git 2.28.0			  07/26/2020			GITTUTORIAL(7)


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