X-Git-Url: https://git.octo.it/?a=blobdiff_plain;f=Documentation%2Ftutorial.txt;h=fa79b016c77a7f37ae1e289eb42bb008174eda81;hb=dcd0409fc545e881a61f522eb8f1d1a7e814eb94;hp=957ea96b83c9f37ba9cc0556438d1fd9a919d2d5;hpb=b43d44779bf98977b211256f936d0edda8a9625a;p=git.git diff --git a/Documentation/tutorial.txt b/Documentation/tutorial.txt index 957ea96b..fa79b016 100644 --- a/Documentation/tutorial.txt +++ b/Documentation/tutorial.txt @@ -1,538 +1,404 @@ -A short git tutorial -==================== -May 2005 +A tutorial introduction to git +============================== +This tutorial explains how to import a new project into git, make +changes to it, and share changes with other developers. -Introduction ------------- +First, note that you can get documentation for a command such as "git +diff" with: -This is trying to be a short tutorial on setting up and using a git -archive, mainly because being hands-on and using explicit examples is -often the best way of explaining what is going on. +------------------------------------------------ +$ man git-diff +------------------------------------------------ -In normal life, most people wouldn't use the "core" git programs -directly, but rather script around them to make them more palatable. -Understanding the core git stuff may help some people get those scripts -done, though, and it may also be instructive in helping people -understand what it is that the higher-level helper scripts are actually -doing. +Importing a new project +----------------------- -The core git is often called "plumbing", with the prettier user -interfaces on top of it called "porcelain". You may not want to use the -plumbing directly very often, but it can be good to know what the -plumbing does for when the porcelain isn't flushing... +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-db +------------------------------------------------ -Creating a git archive ----------------------- +Git will reply -Creating a new git archive couldn't be easier: all git archives start -out empty, and the only thing you need to do is find yourself a -subdirectory that you want to use as a working tree - either an empty -one for a totally new project, or an existing working tree that you want -to import into git. +------------------------------------------------ +defaulting to local storage area +------------------------------------------------ -For our first example, we're going to start a totally new archive from -scratch, with no pre-existing files, and we'll call it "git-tutorial". -To start up, create a subdirectory for it, change into that -subdirectory, and initialize the git infrastructure with "git-init-db": +You've now initialized the working directory--you may notice a new +directory created, named ".git". Tell git that you want it to track +every file under the current directory with - mkdir git-tutorial - cd git-tutorial - git-init-db +------------------------------------------------ +$ git add . +------------------------------------------------ -to which git will reply +Finally, - defaulting to local storage area +------------------------------------------------ +$ git commit -a +------------------------------------------------ -which is just git's way of saying that you haven't been doing anything -strange, and that it will have created a local .git directory setup for -your new project. You will now have a ".git" directory, and you can -inspect that with "ls". For your new empty project, ls should show you -three entries: +will prompt you for a commit message, then record the current state +of all the files to the repository. - - a symlink called HEAD, pointing to "refs/heads/master" +Try modifying some files, then run - Don't worry about the fact that the file that the HEAD link points to - doesn't even exist yet - you haven't created the commit that will - start your HEAD development branch yet. +------------------------------------------------ +$ git diff +------------------------------------------------ - - a subdirectory called "objects", which will contain all the git SHA1 - objects of your project. You should never have any real reason to - look at the objects directly, but you might want to know that these - objects are what contains all the real _data_ in your repository. +to review your changes. When you're done, - - a subdirectory called "refs", which contains references to objects. +------------------------------------------------ +$ git commit -a +------------------------------------------------ - In particular, the "refs" subdirectory will contain two other - subdirectories, named "heads" and "tags" respectively. They do - exactly what their names imply: they contain references to any number - of different "heads" of development (aka "branches"), and to any - "tags" that you have created to name specific versions of your - repository. +will again prompt your for a message describing the change, and then +record the new versions of the modified files. - One note: the special "master" head is the default branch, which is - why the .git/HEAD file was created as a symlink to it even if it - doesn't yet exist. Basically, the HEAD link is supposed to always - point to the branch you are working on right now, and you always - start out expecting to work on the "master" branch. +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. Tools that turn commits into email, for +example, use the first line on the Subject line and the rest of the +commit in the body. - However, this is only a convention, and you can name your branches - anything you want, and don't have to ever even _have_ a "master" - branch. A number of the git tools will assume that .git/HEAD is - valid, though. +To add a new file, first create the file, then - [ Implementation note: an "object" is identified by its 160-bit SHA1 - hash, aka "name", and a reference to an object is always the 40-byte - hex representation of that SHA1 name. The files in the "refs" - subdirectory are expected to contain these hex references (usually - with a final '\n' at the end), and you should thus expect to see a - number of 41-byte files containing these references in this refs - subdirectories when you actually start populating your tree ] +------------------------------------------------ +$ git add path/to/new/file +------------------------------------------------ -You have now created your first git archive. Of course, since it's -empty, that's not very useful, so let's start populating it with data. +then commit as usual. No special command is required when removing a +file; just remove it, then commit. +At any point you can view the history of your changes using - Populating a git archive - ------------------------ +------------------------------------------------ +$ git whatchanged +------------------------------------------------ -We'll keep this simple and stupid, so we'll start off with populating a -few trivial files just to get a feel for it. +If you also want to see complete diffs at each step, use -Start off with just creating any random files that you want to maintain -in your git archive. We'll start off with a few bad examples, just to -get a feel for how this works: +------------------------------------------------ +$ git whatchanged -p +------------------------------------------------ - echo "Hello World" > a - echo "Silly example" > b +Managing branches +----------------- -you have now created two files in your working directory, but to -actually check in your hard work, you will have to go through two steps: +A single git repository can maintain multiple branches of +development. To create a new branch named "experimental", use - - fill in the "cache" aka "index" file with the information about your - working directory state +------------------------------------------------ +$ git branch experimental +------------------------------------------------ - - commit that index file as an object. +If you now run -The first step is trivial: when you want to tell git about any changes -to your working directory, you use the "git-update-cache" program. That -program normally just takes a list of filenames you want to update, but -to avoid trivial mistakes, it refuses to add new entries to the cache -(or remove existing ones) unless you explicitly tell it that you're -adding a new entry with the "--add" flag (or removing an entry with the -"--remove") flag. +------------------------------------------------ +$ git branch +------------------------------------------------ -So to populate the index with the two files you just created, you can do +you'll get a list of all existing branches: - git-update-cache --add a b +------------------------------------------------ + experimental +* master +------------------------------------------------ -and you have now told git to track those two files. +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 -In fact, as you did that, if you now look into your object directory, -you'll notice that git will have added two new objects to the object -store. If you did exactly the steps above, you should now be able to do +------------------------------------------------ +$ git checkout experimental +------------------------------------------------ - ls .git/objects/??/* +to switch to the experimental branch. Now edit a file, commit the +change, and switch back to the master branch: -and see two files: +------------------------------------------------ +(edit file) +$ git commit -a +$ git checkout master +------------------------------------------------ - .git/objects/55/7db03de997c86a4a028e1ebd3a1ceb225be238 - .git/objects/f2/4c74a2e500f5ee1332c86b94199f52b1d1d962 +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. -which correspond with the object with SHA1 names of 557db... and f24c7.. -respectively. +You can make a different change on the master branch: -If you want to, you can use "git-cat-file" to look at those objects, but -you'll have to use the object name, not the filename of the object: +------------------------------------------------ +(edit file) +$ git commit -a +------------------------------------------------ - git-cat-file -t 557db03de997c86a4a028e1ebd3a1ceb225be238 +at this point the two branches have diverged, with different changes +made in each. To merge the changes made in the two branches, run -where the "-t" tells git-cat-file to tell you what the "type" of the -object is. Git will tell you that you have a "blob" object (ie just a -regular file), and you can see the contents with +------------------------------------------------ +$ git pull . experimental +------------------------------------------------ - git-cat-file "blob" 557db03de997c86a4a028e1ebd3a1ceb225be238 +If the changes don't conflict, you're done. If there are conflicts, +markers will be left in the problematic files showing the conflict; -which will print out "Hello World". The object 557db... is nothing -more than the contents of your file "a". +------------------------------------------------ +$ git diff +------------------------------------------------ -[ Digression: don't confuse that object with the file "a" itself. The - object is literally just those specific _contents_ of the file, and - however much you later change the contents in file "a", the object we - just looked at will never change. Objects are immutable. ] +will show this. Once you've edited the files to resolve the +conflicts, -Anyway, as we mentioned previously, you normally never actually take a -look at the objects themselves, and typing long 40-character hex SHA1 -names is not something you'd normally want to do. The above digression -was just to show that "git-update-cache" did something magical, and -actually saved away the contents of your files into the git content -store. +------------------------------------------------ +$ git commit -a +------------------------------------------------ -Updating the cache did something else too: it created a ".git/index" -file. This is the index that describes your current working tree, and -something you should be very aware of. Again, you normally never worry -about the index file itself, but you should be aware of the fact that -you have not actually really "checked in" your files into git so far, -you've only _told_ git about them. +will commit the result of the merge. Finally, -However, since git knows about them, you can now start using some of the -most basic git commands to manipulate the files or look at their status. +------------------------------------------------ +$ gitk +------------------------------------------------ -In particular, let's not even check in the two files into git yet, we'll -start off by adding another line to "a" first: +will show a nice graphical representation of the resulting history. - echo "It's a new day for git" >> a +If you develop on a branch crazy-idea, then regret it, you can always +delete the branch with -and you can now, since you told git about the previous state of "a", ask -git what has changed in the tree compared to your old index, using the -"git-diff-files" command: +------------------------------------- +$ git branch -D crazy-idea +------------------------------------- - git-diff-files +Branches are cheap and easy, so this is a good way to try something +out. -oops. That wasn't very readable. It just spit out its own internal -version of a "diff", but that internal version really just tells you -that it has noticed that "a" has been modified, and that the old object -contents it had have been replaced with something else. +Using git for collaboration +--------------------------- -To make it readable, we can tell git-diff-files to output the -differences as a patch, using the "-p" flag: +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. - git-diff-files -p +Bob begins with: -which will spit out +------------------------------------------------ +$ git clone /home/alice/project myrepo +------------------------------------------------ - diff --git a/a b/a - --- a/a - +++ b/a - @@ -1 +1,2 @@ - Hello World - +It's a new day for git +This creates a new directory "myrepo" containing a clone of Alice's +repository. The clone is on an equal footing with the original +project, posessing its own copy of the original project's history. -ie the diff of the change we caused by adding another line to "a". +Bob then makes some changes and commits them: -In other words, git-diff-files always shows us the difference between -what is recorded in the index, and what is currently in the working -tree. That's very useful. +------------------------------------------------ +(edit files) +$ 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: - Committing git state - -------------------- +------------------------------------------------ +$ cd /home/alice/project +$ git pull /home/bob/myrepo +------------------------------------------------ -Now, we want to go to the next stage in git, which is to take the files -that git knows about in the index, and commit them as a real tree. We do -that in two phases: creating a "tree" object, and committing that "tree" -object as a "commit" object together with an explanation of what the -tree was all about, along with information of how we came to that state. +This actually pulls changes from the branch in Bob's repository named +"master". Alice could request a different branch by adding the name +of the branch to the end of the git pull command line. -Creating a tree object is trivial, and is done with "git-write-tree". -There are no options or other input: git-write-tree will take the -current index state, and write an object that describes that whole -index. In other words, we're now tying together all the different -filenames with their contents (and their permissions), and we're -creating the equivalent of a git "directory" object: +This merges Bob's changes into her repository; "git whatchanged" will +now show the new commits. If Alice has made her own changes in the +meantime, then Bob's changes will be merged in, and she will need to +manually fix any conflicts. - git-write-tree +A more cautious Alice might wish to examine Bob's changes before +pulling them. She can do this by creating a temporary branch just +for the purpose of studying Bob's changes: -and this will just output the name of the resulting tree, in this case -(if you have does exactly as I've described) it should be +------------------------------------- +$ git fetch /home/bob/myrepo master:bob-incoming +------------------------------------- - 3ede4ed7e895432c0a247f09d71a76db53bd0fa4 - -which is another incomprehensible object name. Again, if you want to, -you can use "git-cat-file -t 3ede4.." to see that this time the object -is not a "blob" object, but a "tree" object (you can also use -git-cat-file to actually output the raw object contents, but you'll see -mainly a binary mess, so that's less interesting). - -However - normally you'd never use "git-write-tree" on its own, because -normally you always commit a tree into a commit object using the -"git-commit-tree" command. In fact, it's easier to not actually use -git-write-tree on its own at all, but to just pass its result in as an -argument to "git-commit-tree". - -"git-commit-tree" normally takes several arguments - it wants to know -what the _parent_ of a commit was, but since this is the first commit -ever in this new archive, and it has no parents, we only need to pass in -the tree ID. However, git-commit-tree also wants to get a commit message -on its standard input, and it will write out the resulting ID for the -commit to its standard output. - -And this is where we start using the .git/HEAD file. The HEAD file is -supposed to contain the reference to the top-of-tree, and since that's -exactly what git-commit-tree spits out, we can do this all with a simple -shell pipeline: - - echo "Initial commit" | git-commit-tree $(git-write-tree) > .git/HEAD - -which will say: - - Committing initial tree 3ede4ed7e895432c0a247f09d71a76db53bd0fa4 - -just to warn you about the fact that it created a totally new commit -that is not related to anything else. Normally you do this only _once_ -for a project ever, and all later commits will be parented on top of an -earlier commit, and you'll never see this "Committing initial tree" -message ever again. - - - Making a change - --------------- - -Remember how we did the "git-update-cache" on file "a" and then we -changed "a" afterward, and could compare the new state of "a" with the -state we saved in the index file? - -Further, remember how I said that "git-write-tree" writes the contents -of the _index_ file to the tree, and thus what we just committed was in -fact the _original_ contents of the file "a", not the new ones. We did -that on purpose, to show the difference between the index state, and the -state in the working directory, and how they don't have to match, even -when we commit things. - -As before, if we do "git-diff-files -p" in our git-tutorial project, -we'll still see the same difference we saw last time: the index file -hasn't changed by the act of committing anything. However, now that we -have committed something, we can also learn to use a new command: -"git-diff-cache". - -Unlike "git-diff-files", which showed the difference between the index -file and the working directory, "git-diff-cache" shows the differences -between a committed _tree_ and either the the index file or the working -directory. In other words, git-diff-cache wants a tree to be diffed -against, and before we did the commit, we couldn't do that, because we -didn't have anything to diff against. - -But now we can do - - git-diff-cache -p HEAD - -(where "-p" has the same meaning as it did in git-diff-files), and it -will show us the same difference, but for a totally different reason. -Now we're comparing the working directory not against the index file, -but against the tree we just wrote. It just so happens that those two -are obviously the same, so we get the same result. - -In other words, "git-diff-cache" normally compares a tree against the -working directory, but when given the "--cached" flag, it is told to -instead compare against just the index cache contents, and ignore the -current working directory state entirely. Since we just wrote the index -file to HEAD, doing "git-diff-cache --cached -p HEAD" should thus return -an empty set of differences, and that's exactly what it does. - -[ Digression: "git-diff-cache" really always uses the index for its - comparisons, and saying that it compares a tree against the working - directory is thus not strictly accurate. In particular, the list of - files to compare (the "meta-data") _always_ comes from the index file, - regardless of whether the --cached flag is used or not. The --cached - flag really only determines whether the file _contents_ to be compared - come from the working directory or not. - - This is not hard to understand, as soon as you realize that git simply - never knows (or cares) about files that it is not told about - explicitly. Git will never go _looking_ for files to compare, it - expects you to tell it what the files are, and that's what the index - is there for. ] - -However, our next step is to commit the _change_ we did, and again, to -understand what's going on, keep in mind the difference between "working -directory contents", "index file" and "committed tree". We have changes -in the working directory that we want to commit, and we always have to -work through the index file, so the first thing we need to do is to -update the index cache: - - git-update-cache a - -(note how we didn't need the "--add" flag this time, since git knew -about the file already). - -Note what happens to the different git-diff-xxx versions here. After -we've updated "a" in the index, "git-diff-files -p" now shows no -differences, but "git-diff-cache -p HEAD" still _does_ show that the -current state is different from the state we committed. In fact, now -"git-diff-cache" shows the same difference whether we use the "--cached" -flag or not, since now the index is coherent with the working directory. - -Now, since we've updated "a" in the index, we can commit the new -version. We could do it by writing the tree by hand, and committing the -tree (this time we'd have to use the "-p HEAD" flag to tell commit that -the HEAD was the _parent_ of the new commit, and that this wasn't an -initial commit any more), but the fact is, git has a simple helper -script for doing all of the non-initial commits that does all of this -for you, and starts up an editor to let you write your commit message -yourself, so let's just use that: - - git commit - -Write whatever message you want, and all the lines that start with '#' -will be pruned out, and the rest will be used as the commit message for -the change. If you decide you don't want to commit anything after all at -this point (you can continue to edit things and update the cache), you -can just leave an empty message. Otherwise git-commit-script will commit -the change for you. - -You've now made your first real git commit. And if you're interested in -looking at what git-commit-script really does, feel free to investigate: -it's a few very simple shell scripts to generate the helpful (?) commit -message headers, and a few one-liners that actually do the commit itself. - - - Checking it out - --------------- - -While creating changes is useful, it's even more useful if you can tell -later what changed. The most useful command for this is another of the -"diff" family, namely "git-diff-tree". - -git-diff-tree can be given two arbitrary trees, and it will tell you the -differences between them. Perhaps even more commonly, though, you can -give it just a single commit object, and it will figure out the parent -of that commit itself, and show the difference directly. Thus, to get -the same diff that we've already seen several times, we can now do - - git-diff-tree -p HEAD - -(again, "-p" means to show the difference as a human-readable patch), -and it will show what the last commit (in HEAD) actually changed. - -More interestingly, you can also give git-diff-tree the "-v" flag, which -tells it to also show the commit message and author and date of the -commit, and you can tell it to show a whole series of diffs. -Alternatively, you can tell it to be "silent", and not show the diffs at -all, but just show the actual commit message. - -In fact, together with the "git-rev-list" program (which generates a -list of revisions), git-diff-tree ends up being a veritable fount of -changes. A trivial (but very useful) script called "git-whatchanged" is -included with git which does exactly this, and shows a log of recent -activity. - -To see the whole history of our pitiful little git-tutorial project, you -can do - - git log - -which shows just the log messages, or if we want to see the log together -with the associated patches use the more complex (and much more -powerful) - - git-whatchanged -p --root +which fetches the changes from Bob's master branch into a new branch +named bob-incoming. (Unlike git pull, git fetch just fetches a copy +of Bob's line of development without doing any merging). Then -and you will see exactly what has changed in the repository over its -short history. - -[ Side note: the "--root" flag is a flag to git-diff-tree to tell it to - show the initial aka "root" commit too. Normally you'd probably not - want to see the initial import diff, but since the tutorial project - was started from scratch and is so small, we use it to make the result - a bit more interesting ] +------------------------------------- +$ git whatchanged -p master..bob-incoming +------------------------------------- -With that, you should now be having some inkling of what git does, and -can explore on your own. +shows a list of all the changes that Bob made since he branched from +Alice's master branch. +After examing those changes, and possibly fixing things, Alice can +pull the changes into her master branch: - Copying archives - ----------------- +------------------------------------- +$ git checkout master +$ git pull . bob-incoming +------------------------------------- -Git archives are normally totally self-sufficient, and it's worth noting -that unlike CVS, for example, there is no separate notion of -"repository" and "working tree". A git repository normally _is_ the -working tree, with the local git information hidden in the ".git" -subdirectory. There is nothing else. What you see is what you got. +The last command is a pull from the "bob-incoming" branch in Alice's +own repository. -[ Side note: you can tell git to split the git internal information from - the directory that it tracks, but we'll ignore that for now: it's not - how normal projects work, and it's really only meant for special uses. - So the mental model of "the git information is always tied directly to - the working directory that it describes" may not be technically 100% - accurate, but it's a good model for all normal use ] +Later, Bob can update his repo with Alice's latest changes using -This has two implications: +------------------------------------- +$ git pull +------------------------------------- - - if you grow bored with the tutorial archive you created (or you've - made a mistake and want to start all over), you can just do simple +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 file .git/remotes/origin, and that location is used +as the default for pulls. - rm -rf git-tutorial +Bob may also notice a branch in his repository that he didn't create: - and it will be gone. There's no external repository, and there's no - history outside of the project you created. +------------------------------------- +$ git branch +* master + origin +------------------------------------- - - if you want to move or duplicate a git archive, you can do so. There - is no "git clone" command: if you want to create a copy of your - archive (with all the full history that went along with it), you can - do so with a regular "cp -a git-tutorial new-git-tutorial". +The "origin" branch, which was created automatically by "git clone", +is a pristine copy of Alice's master branch; Bob should never commit +to it. - Note that when you've moved or copied a git archive, your git index - file (which caches various information, notably some of the "stat" - information for the files involved) will likely need to be refreshed. - So after you do a "cp -a" to create a new copy, you'll want to do +If Bob later decides to work from a different host, he can still +perform clones and pulls using the ssh protocol: - git-update-cache --refresh +------------------------------------- +$ git clone alice.org:/home/alice/project myrepo +------------------------------------- - to make sure that the index file is up-to-date in the new one. +Alternatively, git has a native protocol, or can use rsync or http; +see gitlink:git-pull[1] for details. -Note that the second point is true even across machines. You can -duplicate a remote git archive with _any_ regular copy mechanism, be it -"scp", "rsync" or "wget". +Git can also be used in a CVS-like mode, with a central repository +that various users push changes to; see gitlink:git-push[1] and +link:cvs-migration.html[git for CVS users]. -When copying a remote repository, you'll want to at a minimum update the -index cache when you do this, and especially with other peoples -repositories you often want to make sure that the index cache is in some -known state (you don't know _what_ they've done and not yet checked in), -so usually you'll precede the "git-update-cache" with a +Keeping track of history +------------------------ - git-read-tree --reset HEAD - git-update-cache --refresh +Git history is represented as a series of interrelated commits. The +most recent commit in the currently checked-out branch can always be +referred to as HEAD, and the "parent" of any commit can always be +referred to by appending a caret, "^", to the end of the name of the +commit. So, for example, -which will force a total index re-build from the tree pointed to by HEAD -(it resets the index contents to HEAD, and then the git-update-cache -makes sure to match up all index entries with the checked-out files). +------------------------------------- +git diff HEAD^ HEAD +------------------------------------- -The above can also be written as simply +shows the difference between the most-recently checked-in state of +the tree and the previous state, and - git reset +------------------------------------- +git diff HEAD^^ HEAD^ +------------------------------------- -and in fact a lot of the common git command combinations can be scripted -with the "git xyz" interfaces, and you can learn things by just looking -at what the git-*-script scripts do ("git reset" is the above two lines -implemented in "git-reset-script", but some things like "git status" and -"git commit" are slightly more complex scripts around the basic git -commands). +shows the difference between that previous state and the state two +commits ago. Also, HEAD~5 can be used as a shorthand for HEAD{caret}{caret}{caret}{caret}{caret}, +and more generally HEAD~n can refer to the nth previous commit. +Commits representing merges have more than one parent, and you can +specify which parent to follow in that case; see +gitlink:git-rev-parse[1]. -NOTE! Many (most?) public remote repositories will not contain any of -the checked out files or even an index file, and will _only_ contain the -actual core git files. Such a repository usually doesn't even have the -".git" subdirectory, but has all the git files directly in the -repository. +The name of a branch can also be used to refer to the most recent +commit on that branch; so you can also say things like -To create your own local live copy of such a "raw" git repository, you'd -first create your own subdirectory for the project, and then copy the -raw repository contents into the ".git" directory. For example, to -create your own copy of the git repository, you'd do the following +------------------------------------- +git diff HEAD experimental +------------------------------------- - mkdir my-git - cd my-git - rsync -rL rsync://rsync.kernel.org/pub/scm/linux/kernel/git/torvalds/git.git/ .git +to see the difference between the most-recently committed tree in +the current branch and the most-recently committed tree in the +experimental branch. -followed by +But you may find it more useful to see the list of commits made in +the experimental branch but not in the current branch, and - git-read-tree HEAD +------------------------------------- +git whatchanged HEAD..experimental +------------------------------------- -to populate the index. However, now you have populated the index, and -you have all the git internal files, but you will notice that you don't -actually have any of the _working_directory_ files to work on. To get -those, you'd check them out with +will do that, just as - git-checkout-cache -u -a +------------------------------------- +git whatchanged experimental..HEAD +------------------------------------- -where the "-u" flag means that you want the checkout to keep the index -up-to-date (so that you don't have to refresh it afterward), and the -"-a" file means "check out all files" (if you have a stale copy or an -older version of a checked out tree you may also need to add the "-f" -file first, to tell git-checkout-cache to _force_ overwriting of any old -files). +will show the list of commits made on the HEAD but not included in +experimental. -You have now successfully copied somebody else's (mine) remote -repository, and checked it out. +You can also give commits convenient names of your own: after running -[ to be continued.. cvs2git, tagging versions, branches, merging.. ] +------------------------------------- +$ git-tag v2.5 HEAD^^ +------------------------------------- + +you can refer to HEAD^^ 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 +gitlink:git-tag[1] for details. + +You can revisit the old state of a tree, and make further +modifications if you wish, using git branch: the command + +------------------------------------- +$ git branch stable-release v2.5 +------------------------------------- + +will create a new branch named "stable-release" starting from the +commit which you tagged with the name v2.5. + +You can reset the state of any branch to an earlier commit at any +time with + +------------------------------------- +$ git reset --hard v2.5 +------------------------------------- + +This will remove all later commits from this branch and reset the +working tree to the state it had when the given commit was made. If +this branch is the only branch containing the later commits, those +later changes will be lost. Don't use "git reset" on a +publicly-visible branch that other developers pull from, as git will +be confused by history that disappears in this way. + +Next Steps +---------- + +Some good commands to explore next: + + * gitlink:git-diff[1]: This flexible command does much more than + we've seen in the few examples above. + + * gitlink:git-format-patch[1], gitlink: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. + + * gitlink: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. + +Other good starting points include link:everyday.html[Everday GIT +with 20 Commands Or So] and link:cvs-migration.html[git for CVS +users]. Also, link:core-tutorial.html[A short git tutorial] gives an +introduction to lower-level git commands for advanced users and +developers.