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diff --git a/Documentation/gitcore-tutorial.txt b/Documentation/gitcore-tutorial.txt index 7ba5e589d7..3a0ec8c53a 100644 --- a/Documentation/gitcore-tutorial.txt +++ b/Documentation/gitcore-tutorial.txt @@ -3,7 +3,7 @@ gitcore-tutorial(7) NAME ---- -gitcore-tutorial - A git core tutorial for developers +gitcore-tutorial - A Git core tutorial for developers SYNOPSIS -------- @@ -12,39 +12,47 @@ git * DESCRIPTION ----------- -This tutorial explains how to use the "core" git programs to set up and -work with a git repository. +This tutorial explains how to use the "core" Git commands to set up and +work with a Git repository. -If you just need to use git as a revision control system you may prefer -to start with "A Tutorial Introduction to GIT" (linkgit:gittutorial[7]) or -link:user-manual.html[the GIT User Manual]. +If you just need to use Git as a revision control system you may prefer +to start with "A Tutorial Introduction to Git" (linkgit:gittutorial[7]) or +link:user-manual.html[the Git User Manual]. However, an understanding of these low-level tools can be helpful if -you want to understand git's internals. +you want to understand Git's internals. -The core git is often called "plumbing", with the prettier user +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. +plumbing does when the porcelain isn't flushing. + +Back when this document was originally written, many porcelain +commands were shell scripts. For simplicity, it still uses them as +examples to illustrate how plumbing is fit together to form the +porcelain commands. The source tree includes some of these scripts in +contrib/examples/ for reference. Although these are not implemented as +shell scripts anymore, the description of what the plumbing layer +commands do is still valid. [NOTE] Deeper technical details are often marked as Notes, which you can skip on your first reading. -Creating a git repository +Creating a Git repository ------------------------- -Creating a new git repository couldn't be easier: all git repositories start +Creating a new Git repository couldn't be easier: all Git repositories 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. +to import into Git. For our first example, we're going to start a totally new repository 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': +subdirectory, and initialize the Git infrastructure with 'git init': ------------------------------------------------ $ mkdir git-tutorial @@ -52,13 +60,13 @@ $ cd git-tutorial $ git init ------------------------------------------------ -to which git will reply +to which Git will reply ---------------- Initialized empty Git repository in .git/ ---------------- -which is just git's way of saying that you haven't been doing anything +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, it should show you @@ -94,15 +102,15 @@ start out expecting to work on the `master` branch. 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 +branch. A number of the Git tools will assume that `.git/HEAD` is valid, though. [NOTE] -An 'object' is identified by its 160-bit SHA1 hash, aka 'object name', +An 'object' is identified by its 160-bit SHA-1 hash, aka 'object name', and a reference to an object is always the 40-byte hex -representation of that SHA1 name. The files in the `refs` +representation of that SHA-1 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 +(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 these `refs` subdirectories when you actually start populating your tree. @@ -111,18 +119,18 @@ populating your tree. An advanced user may want to take a look at linkgit:gitrepository-layout[5] after finishing this tutorial. -You have now created your first git repository. Of course, since it's +You have now created your first Git repository. Of course, since it's empty, that's not very useful, so let's start populating it with data. -Populating a git repository +Populating a Git repository --------------------------- 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. Start off with just creating any random files that you want to maintain -in your git repository. We'll start off with a few bad examples, just to +in your Git repository. We'll start off with a few bad examples, just to get a feel for how this works: ------------------------------------------------ @@ -138,13 +146,13 @@ but to actually check in your hard work, you will have to go through two steps: - commit that index file as an object. -The first step is trivial: when you want to tell git about any changes -to your working tree, you use the 'git-update-index' program. That +The first step is trivial: when you want to tell Git about any changes +to your working tree, you use the 'git update-index' 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 index (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. +adding a new entry with the `--add` flag (or removing an entry with the +`--remove`) flag. So to populate the index with the two files you just created, you can do @@ -152,10 +160,10 @@ So to populate the index with the two files you just created, you can do $ git update-index --add hello example ------------------------------------------------ -and you have now told git to track those two files. +and you have now told Git to track those two files. 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 +you'll notice that Git will have added two new objects to the object database. If you did exactly the steps above, you should now be able to do @@ -173,19 +181,19 @@ and see two files: which correspond with the objects with names of `557db...` and `f24c7...` respectively. -If you want to, you can use 'git-cat-file' to look at those objects, but +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: ---------------- $ git cat-file -t 557db03de997c86a4a028e1ebd3a1ceb225be238 ---------------- -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 (i.e., just a +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 (i.e., just a regular file), and you can see the contents with ---------------- -$ git cat-file "blob" 557db03 +$ git cat-file blob 557db03 ---------------- which will print out "Hello World". The object `557db03` is nothing @@ -205,30 +213,30 @@ hexadecimal digits in most places. Anyway, as we mentioned previously, you normally never actually take a look at the objects themselves, and typing long 40-character hex names is not something you'd normally want to do. The above digression -was just to show that 'git-update-index' did something magical, and -actually saved away the contents of your files into the git object +was just to show that 'git update-index' did something magical, and +actually saved away the contents of your files into the Git object database. Updating the index 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. +you have not actually really "checked in" your files into Git so far, +you've only *told* Git about them. -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. +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. -In particular, let's not even check in the two files into git yet, we'll +In particular, let's not even check in the two files into Git yet, we'll start off by adding another line to `hello` first: ------------------------------------------------ $ echo "It's a new day for git" >>hello ------------------------------------------------ -and you can now, since you told git about the previous state of `hello`, ask -git what has changed in the tree compared to your old index, using the -'git-diff-files' command: +and you can now, since you told Git about the previous state of `hello`, ask +Git what has changed in the tree compared to your old index, using the +'git diff-files' command: ------------ $ git diff-files @@ -239,7 +247,7 @@ version of a 'diff', but that internal version really just tells you that it has noticed that "hello" has been modified, and that the old object contents it had have been replaced with something else. -To make it readable, we can tell 'git-diff-files' to output the +To make it readable, we can tell 'git diff-files' to output the differences as a patch, using the `-p` flag: ------------ @@ -251,11 +259,11 @@ index 557db03..263414f 100644 @@ -1 +1,2 @@ Hello World +It's a new day for git ----- +------------ i.e. the diff of the change we caused by adding another line to `hello`. -In other words, 'git-diff-files' always shows us the difference between +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. @@ -274,21 +282,21 @@ index 557db03..263414f 100644 ------------ -Committing git state +Committing Git state -------------------- -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 +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. -Creating a tree object is trivial, and is done with 'git-write-tree'. +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: +creating the equivalent of a Git "directory" object: ------------------------------------------------ $ git write-tree @@ -302,28 +310,28 @@ and this will just output the name of the resulting tree, in this case ---------------- which is another incomprehensible object name. Again, if you want to, -you can use `git cat-file -t 8988d\...` to see that this time the object +you can use `git cat-file -t 8988d...` 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 +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' 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 +'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 repository, and it has no parents, we only need to pass in -the object name of the tree. However, 'git-commit-tree' also wants to get a +the object name of the tree. However, 'git commit-tree' also wants to get a commit message on its standard input, and it will write out the resulting object name for the commit to its standard output. And this is where we create the `.git/refs/heads/master` file which is pointed at by `HEAD`. This file is supposed to contain the reference to the top-of-tree of the master branch, and since -that's exactly what 'git-commit-tree' spits out, we can do this +that's exactly what 'git commit-tree' spits out, we can do this all with a sequence of simple shell commands: ------------------------------------------------ @@ -345,11 +353,11 @@ instead, and it would have done the above magic scripting for you. Making a change --------------- -Remember how we did the 'git-update-index' on file `hello` and then we +Remember how we did the 'git update-index' on file `hello` and then we changed `hello` afterward, and could compare the new state of `hello` with the state we saved in the index file? -Further, remember how I said that 'git-write-tree' writes the contents +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 `hello`, not the new ones. We did that on purpose, to show the difference between the index state, and the @@ -360,12 +368,12 @@ 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-index'. +'git diff-index'. -Unlike 'git-diff-files', which showed the difference between the index -file and the working tree, 'git-diff-index' shows the differences +Unlike 'git diff-files', which showed the difference between the index +file and the working tree, 'git diff-index' shows the differences between a committed *tree* and either the index file or the working -tree. In other words, 'git-diff-index' wants a tree to be diffed +tree. In other words, 'git diff-index' 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. @@ -375,7 +383,7 @@ But now we can do $ git diff-index -p HEAD ---------------- -(where `-p` has the same meaning as it did in 'git-diff-files'), and it +(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 tree not against the index file, but against the tree we just wrote. It just so happens that those two @@ -390,26 +398,26 @@ $ git diff HEAD which ends up doing the above for you. -In other words, 'git-diff-index' normally compares a tree against the -working tree, but when given the `\--cached` flag, it is told to +In other words, 'git diff-index' normally compares a tree against the +working tree, but when given the `--cached` flag, it is told to instead compare against just the index cache contents, and ignore the current working tree state entirely. Since we just wrote the index -file to HEAD, doing `git diff-index \--cached -p HEAD` should thus return +file to HEAD, doing `git diff-index --cached -p HEAD` should thus return an empty set of differences, and that's exactly what it does. [NOTE] ================ -'git-diff-index' really always uses the index for its +'git diff-index' really always uses the index for its comparisons, and saying that it compares a tree against the working tree 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` +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 tree or not. -This is not hard to understand, as soon as you realize that git simply +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 +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. ================ @@ -425,14 +433,14 @@ update the index cache: $ git update-index hello ------------------------------------------------ -(note how we didn't need the `\--add` flag this time, since git knew +(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-\*' versions here. After -we've updated `hello` in the index, `git diff-files -p` now shows no +Note what happens to the different 'git diff-{asterisk}' versions here. +After we've updated `hello` in the index, `git diff-files -p` now shows no differences, but `git diff-index -p HEAD` still *does* show that the current state is different from the state we committed. In fact, now -'git-diff-index' shows the same difference whether we use the `--cached` +'git diff-index' shows the same difference whether we use the `--cached` flag or not, since now the index is coherent with the working tree. Now, since we've updated `hello` in the index, we can commit the new @@ -456,11 +464,11 @@ this point (you can continue to edit things and update the index), you can just leave an empty message. Otherwise `git commit` will commit the change for you. -You've now made your first real git commit. And if you're interested in +You've now made your first real Git commit. And if you're interested in looking at what `git commit` 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 ('git-commit'). +commit itself ('git commit'). Inspecting Changes @@ -468,9 +476,9 @@ Inspecting Changes 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'. +'diff' family, namely 'git diff-tree'. -'git-diff-tree' can be given two arbitrary trees, and it will tell you the +'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 @@ -486,7 +494,7 @@ and it will show what the last commit (in `HEAD`) actually changed. [NOTE] ============ Here is an ASCII art by Jon Loeliger that illustrates how -various diff-\* commands compare things. +various 'diff-{asterisk}' commands compare things. diff-tree +----+ @@ -518,56 +526,23 @@ various diff-\* commands compare things. +-----------+ ============ -More interestingly, you can also give 'git-diff-tree' the `--pretty` flag, +More interestingly, you can also give 'git diff-tree' the `--pretty` 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 -activities. - -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 ----------------- - -and you will see exactly what has changed in the repository over its -short history. - -[NOTE] -When using the above two commands, the initial commit will be shown. -If this is a problem because it is huge, you can hide it by setting -the log.showroot configuration variable to false. Having this, you -can still show it for each command just adding the `\--root` option, -which is a flag for 'git-diff-tree' accepted by both commands. - -With that, you should now be having some inkling of what git does, and -can explore on your own. - -[NOTE] -Most likely, you are not directly using the core -git Plumbing commands, but using Porcelain such as 'git-add', `git-rm' -and `git-commit'. +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. You can emulate `git log`, `git log -p`, etc. with a trivial +script that pipes the output of `git rev-list` to `git diff-tree --stdin`, +which was exactly how early versions of `git log` were implemented. Tagging a version ----------------- -In git, there are two kinds of tags, a "light" one, and an "annotated tag". +In Git, there are two kinds of tags, a "light" one, and an "annotated tag". A "light" tag is technically nothing more than a branch, except we put it in the `.git/refs/tags/` subdirectory instead of calling it a `head`. @@ -590,19 +565,19 @@ obviously be an empty diff, but if you continue to develop and commit stuff, you can use your tag as an "anchor-point" to see what has changed since you tagged it. -An "annotated tag" is actually a real git object, and contains not only a +An "annotated tag" is actually a real Git object, and contains not only a pointer to the state you want to tag, but also a small tag name and message, along with optionally a PGP signature that says that yes, you really did that tag. You create these annotated tags with either the `-a` or -`-s` flag to 'git-tag': +`-s` flag to 'git tag': ---------------- $ git tag -s <tagname> ---------------- which will sign the current `HEAD` (but you can also give it another -argument that specifies the thing to tag, i.e., you could have tagged the +argument that specifies the thing to tag, e.g., you could have tagged the current `mybranch` point by using `git tag <tagname> mybranch`). You normally only do signed tags for major releases or things @@ -615,17 +590,17 @@ name for the state at that point. Copying repositories -------------------- -git repositories are normally totally self-sufficient and relocatable. +Git repositories are normally totally self-sufficient and relocatable. 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` +"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. [NOTE] -You can tell git to split the git internal information from +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 +So the mental model of "the Git information is always tied directly to the working tree that it describes" may not be technically 100% accurate, but it's a good model for all normal use. @@ -641,13 +616,13 @@ $ rm -rf git-tutorial and it will be gone. There's no external repository, and there's no history outside the project you created. - - if you want to move or duplicate a git repository, you can do so. There - is 'git-clone' command, but if all you want to do is just to + - if you want to move or duplicate a Git repository, you can do so. There + is 'git clone' command, but if all you want to do is just to create a copy of your repository (with all the full history that went along with it), you can do so with a regular `cp -a git-tutorial new-git-tutorial`. + -Note that when you've moved or copied a git repository, your git index +Note that when you've moved or copied a Git repository, 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 @@ -659,14 +634,14 @@ $ git update-index --refresh in the new repository to make sure that the index file is up-to-date. Note that the second point is true even across machines. You can -duplicate a remote git repository with *any* regular copy mechanism, be it +duplicate a remote Git repository with *any* regular copy mechanism, be it 'scp', 'rsync' or 'wget'. 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-index' with a +so usually you'll precede the 'git update-index' with a ---------------- $ git read-tree --reset HEAD @@ -674,7 +649,7 @@ $ git update-index --refresh ---------------- 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-index' +It resets the index contents to `HEAD`, and then the 'git update-index' makes sure to match up all index entries with the checked-out files. If the original repository had uncommitted changes in its working tree, `git update-index --refresh` notices them and @@ -686,23 +661,23 @@ The above can also be written as simply $ git reset ---------------- -and in fact a lot of the common git command combinations can be scripted +and in fact a lot of the common Git command combinations can be scripted with the `git xyz` interfaces. You can learn things by just looking at what the various git scripts do. For example, `git reset` used to be -the above two lines implemented in 'git-reset', but some things like -'git-status' and 'git-commit' are slightly more complex scripts around -the basic git commands. +the above two lines implemented in 'git reset', but some things like +'git status' and 'git commit' are slightly more complex scripts around +the basic Git commands. 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 +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. -To create your own local live copy of such a "raw" git repository, you'd +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 +create your own copy of the Git repository, you'd do the following ---------------- $ mkdir my-git @@ -717,7 +692,7 @@ $ git read-tree HEAD ---------------- 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 +you have all the Git internal files, but you will notice that you don't actually have any of the working tree files to work on. To get those, you'd check them out with @@ -729,13 +704,13 @@ 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` flag 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` -flag first, to tell 'git-checkout-index' to *force* overwriting of any old +flag first, to tell 'git checkout-index' to *force* overwriting of any old files). Again, this can all be simplified with ---------------- -$ git clone rsync://rsync.kernel.org/pub/scm/git/git.git/ my-git +$ git clone git://git.kernel.org/pub/scm/git/git.git/ my-git $ cd my-git $ git checkout ---------------- @@ -749,13 +724,13 @@ repository, and checked it out. Creating a new branch --------------------- -Branches in git are really nothing more than pointers into the git +Branches in Git are really nothing more than pointers into the Git object database from within the `.git/refs/` subdirectory, and as we already discussed, the `HEAD` branch is nothing but a symlink to one of these object pointers. You can at any time create a new branch by just picking an arbitrary -point in the project history, and just writing the SHA1 name of that +point in the project history, and just writing the SHA-1 name of that object into a file under `.git/refs/heads/`. You can use any filename you want (and indeed, subdirectories), but the convention is that the "normal" branch is called `master`. That's just a convention, though, @@ -776,7 +751,7 @@ to it. ================================================ If you make the decision to start your new branch at some other point in the history than the current `HEAD`, you can do so by -just telling 'git-checkout' what the base of the checkout would be. +just telling 'git checkout' what the base of the checkout would be. In other words, if you have an earlier tag or branch, you'd just do ------------ @@ -819,7 +794,7 @@ $ git branch <branchname> [startingpoint] which will simply _create_ the branch, but will not do anything further. You can then later -- once you decide that you want to actually develop -on that branch -- switch to that branch with a regular 'git-checkout' +on that branch -- switch to that branch with a regular 'git checkout' with the branchname as the argument. @@ -841,7 +816,7 @@ $ git commit -m "Some work." -i hello Here, we just added another line to `hello`, and we used a shorthand for doing both `git update-index hello` and `git commit` by just giving the filename directly to `git commit`, with an `-i` flag (it tells -git to 'include' that file in addition to what you have done to +Git to 'include' that file in addition to what you have done to the index file so far when making the commit). The `-m` flag is to give the commit log message from the command line. @@ -873,7 +848,7 @@ helps you view what's going on: $ gitk --all ---------------- -will show you graphically both of your branches (that's what the `\--all` +will show you graphically both of your branches (that's what the `--all` means: normally it will just show you your current `HEAD`) and their histories. You can also see exactly how they came to be from a common source. @@ -881,7 +856,7 @@ source. Anyway, let's exit 'gitk' (`^Q` or the File menu), and decide that we want to merge the work we did on the `mybranch` branch into the `master` branch (which is currently our `HEAD` too). To do that, there's a nice -script called 'git-merge', which wants to know which branches you want +script called 'git merge', which wants to know which branches you want to resolve and what the merge is all about: ------------ @@ -892,7 +867,7 @@ where the first argument is going to be used as the commit message if the merge can be resolved automatically. Now, in this case we've intentionally created a situation where the -merge will need to be fixed up by hand, though, so git will do as much +merge will need to be fixed up by hand, though, so Git will do as much of it as it can automatically (which in this case is just merge the `example` file, which had no differences in the `mybranch` branch), and say: @@ -925,13 +900,13 @@ $ git commit -i hello which will very loudly warn you that you're now committing a merge (which is correct, so never mind), and you can write a small merge -message about your adventures in 'git-merge'-land. +message about your adventures in 'git merge'-land. -After you're done, start up `gitk \--all` to see graphically what the +After you're done, start up `gitk --all` to see graphically what the history looks like. Notice that `mybranch` still exists, and you can switch to it, and continue to work with it if you want to. The `mybranch` branch will not contain the merge, but next time you merge it -from the `master` branch, git will know how you merged it, so you'll not +from the `master` branch, Git will know how you merged it, so you'll not have to do _that_ merge again. Another useful tool, especially if you do not always work in X-Window @@ -948,12 +923,11 @@ $ git show-branch --topo-order --more=1 master mybranch ------------------------------------------------ The first two lines indicate that it is showing the two branches -and the first line of the commit log message from their -top-of-the-tree commits, you are currently on `master` branch -(notice the asterisk `\*` character), and the first column for -the later output lines is used to show commits contained in the +with the titles of their top-of-the-tree commits, you are currently on +`master` branch (notice the asterisk `*` character), and the first +column for the later output lines is used to show commits contained in the `master` branch, and the second column for the `mybranch` -branch. Three commits are shown along with their log messages. +branch. Three commits are shown along with their titles. All of them have non blank characters in the first column (`*` shows an ordinary commit on the current branch, `-` is a merge commit), which means they are now part of the `master` branch. Only the "Some @@ -963,25 +937,25 @@ commits from the master branch. The string inside brackets before the commit log message is a short name you can use to name the commit. In the above example, 'master' and 'mybranch' are branch heads. 'master^' is the first parent of 'master' -branch head. Please see linkgit:git-rev-parse[1] if you want to +branch head. Please see linkgit:gitrevisions[7] if you want to see more complex cases. [NOTE] -Without the '--more=1' option, 'git-show-branch' would not output the +Without the '--more=1' option, 'git show-branch' would not output the '[master^]' commit, as '[mybranch]' commit is a common ancestor of both 'master' and 'mybranch' tips. Please see linkgit:git-show-branch[1] for details. [NOTE] If there were more commits on the 'master' branch after the merge, the -merge commit itself would not be shown by 'git-show-branch' by -default. You would need to provide '--sparse' option to make the +merge commit itself would not be shown by 'git show-branch' by +default. You would need to provide `--sparse` option to make the merge commit visible in this case. Now, let's pretend you are the one who did all the work in `mybranch`, and the fruit of your hard work has finally been merged to the `master` branch. Let's go back to `mybranch`, and run -'git-merge' to get the "upstream changes" back to your branch. +'git merge' to get the "upstream changes" back to your branch. ------------ $ git checkout mybranch @@ -993,19 +967,19 @@ would be different) ---------------- Updating from ae3a2da... to a80b4aa.... -Fast forward (no commit created; -m option ignored) - example | 1 + - hello | 1 + - 2 files changed, 2 insertions(+), 0 deletions(-) +Fast-forward (no commit created; -m option ignored) + example | 1 + + hello | 1 + + 2 files changed, 2 insertions(+) ---------------- Because your branch did not contain anything more than what had already been merged into the `master` branch, the merge operation did not actually do a merge. Instead, it just updated the top of the tree of your branch to that of the `master` branch. This is -often called 'fast forward' merge. +often called 'fast-forward' merge. -You can run `gitk \--all` again to see how the commit ancestry +You can run `gitk --all` again to see how the commit ancestry looks like, or run 'show-branch', which tells you this. ------------------------------------------------ @@ -1021,14 +995,14 @@ Merging external work --------------------- It's usually much more common that you merge with somebody else than -merging with your own branches, so it's worth pointing out that git +merging with your own branches, so it's worth pointing out that Git makes that very easy too, and in fact, it's not that different from -doing a 'git-merge'. In fact, a remote merge ends up being nothing +doing a 'git merge'. In fact, a remote merge ends up being nothing more than "fetch the work from a remote repository into a temporary tag" -followed by a 'git-merge'. +followed by a 'git merge'. Fetching from a remote repository is done by, unsurprisingly, -'git-fetch': +'git fetch': ---------------- $ git fetch <remote-repository> @@ -1037,20 +1011,6 @@ $ git fetch <remote-repository> One of the following transports can be used to name the repository to download from: -Rsync:: - `rsync://remote.machine/path/to/repo.git/` -+ -Rsync transport is usable for both uploading and downloading, -but is completely unaware of what git does, and can produce -unexpected results when you download from the public repository -while the repository owner is uploading into it via `rsync` -transport. Most notably, it could update the files under -`refs/` which holds the object name of the topmost commits -before uploading the files in `objects/` -- the downloader would -obtain head commit object name while that object itself is still -not available in the repository. For this reason, it is -considered deprecated. - SSH:: `remote.machine:/path/to/repo.git/` or + @@ -1061,7 +1021,7 @@ and requires you to have a log-in privilege over `ssh` to the remote machine. It finds out the set of objects the other side lacks by exchanging the head commits both ends have and transfers (close to) minimum set of objects. It is by far the -most efficient way to exchange git objects between repositories. +most efficient way to exchange Git objects between repositories. Local directory:: `/path/to/repo.git/` @@ -1070,7 +1030,7 @@ This transport is the same as SSH transport but uses 'sh' to run both ends on the local machine instead of running other end on the remote machine via 'ssh'. -git Native:: +Git Native:: `git://remote.machine/path/to/repo.git/` + This transport was designed for anonymous downloading. Like SSH @@ -1084,7 +1044,7 @@ Downloader from http and https URL first obtains the topmost commit object name from the remote site by looking at the specified refname under `repo.git/refs/` directory, and then tries to obtain the -commit object by downloading from `repo.git/objects/xx/xxx\...` +commit object by downloading from `repo.git/objects/xx/xxx...` using the object name of that commit object. Then it reads the commit object to find out its parent commits and the associate tree object; it repeats this process until it gets all the @@ -1092,10 +1052,10 @@ necessary objects. Because of this behavior, they are sometimes also called 'commit walkers'. + The 'commit walkers' are sometimes also called 'dumb -transports', because they do not require any git aware smart -server like git Native transport does. Any stock HTTP server +transports', because they do not require any Git aware smart +server like Git Native transport does. Any stock HTTP server that does not even support directory index would suffice. But -you must prepare your repository with 'git-update-server-info' +you must prepare your repository with 'git update-server-info' to help dumb transport downloaders. Once you fetch from the remote repository, you `merge` that @@ -1115,7 +1075,7 @@ argument. [NOTE] You could do without using any branches at all, by keeping as many local repositories as you would like to have -branches, and merging between them with 'git-pull', just like +branches, and merging between them with 'git pull', just like you merge between branches. The advantage of this approach is that it lets you keep a set of files for each `branch` checked out and you may find it easier to switch back and forth if you @@ -1132,7 +1092,7 @@ like this: $ git config remote.linus.url http://www.kernel.org/pub/scm/git/git.git/ ------------------------------------------------ -and use the "linus" keyword with 'git-pull' instead of the full URL. +and use the "linus" keyword with 'git pull' instead of the full URL. Examples. @@ -1168,7 +1128,7 @@ $ git show-branch --more=2 master mybranch +* [master^] Some fun. ------------ -Remember, before running 'git-merge', our `master` head was at +Remember, before running 'git merge', our `master` head was at "Some fun." commit, while our `mybranch` head was at "Some work." commit. @@ -1186,16 +1146,16 @@ $ git show-branch * [master] Some fun. ! [mybranch] Some work. -- - + [mybranch] Some work. * [master] Some fun. -*+ [mybranch^] New day. + + [mybranch] Some work. +*+ [master^] Initial commit ------------ Now we are ready to experiment with the merge by hand. `git merge` command, when merging two branches, uses 3-way merge algorithm. First, it finds the common ancestor between them. -The command it uses is 'git-merge-base': +The command it uses is 'git merge-base': ------------ $ mb=$(git merge-base HEAD mybranch) @@ -1204,11 +1164,11 @@ $ mb=$(git merge-base HEAD mybranch) The command writes the commit object name of the common ancestor to the standard output, so we captured its output to a variable, because we will be using it in the next step. By the way, the common -ancestor commit is the "New day." commit in this case. You can +ancestor commit is the "Initial commit" commit in this case. You can tell it by: ------------ -$ git name-rev $mb +$ git name-rev --name-only --tags $mb my-first-tag ------------ @@ -1219,14 +1179,14 @@ this: $ git read-tree -m -u $mb HEAD mybranch ------------ -This is the same 'git-read-tree' command we have already seen, +This is the same 'git read-tree' command we have already seen, but it takes three trees, unlike previous examples. This reads the contents of each tree into different 'stage' in the index file (the first tree goes to stage 1, the second to stage 2, etc.). After reading three trees into three stages, the paths that are the same in all three stages are 'collapsed' into stage 0. Also paths that are the same in two of three stages are -collapsed into stage 0, taking the SHA1 from either stage 2 or +collapsed into stage 0, taking the SHA-1 from either stage 2 or stage 3, whichever is different from stage 1 (i.e. only one side changed from the common ancestor). @@ -1237,8 +1197,8 @@ inspect the index file with this command: ------------ $ git ls-files --stage 100644 7f8b141b65fdcee47321e399a2598a235a032422 0 example -100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello -100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello +100644 557db03de997c86a4a028e1ebd3a1ceb225be238 1 hello +100644 ba42a2a96e3027f3333e13ede4ccf4498c3ae942 2 hello 100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello ------------ @@ -1249,19 +1209,19 @@ this 'collapsing' tends to trivially merge most of the paths fairly quickly, leaving only a handful of real changes in non-zero stages. -To look at only non-zero stages, use `\--unmerged` flag: +To look at only non-zero stages, use `--unmerged` flag: ------------ $ git ls-files --unmerged -100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello -100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello +100644 557db03de997c86a4a028e1ebd3a1ceb225be238 1 hello +100644 ba42a2a96e3027f3333e13ede4ccf4498c3ae942 2 hello 100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello ------------ The next step of merging is to merge these three versions of the file, using 3-way merge. This is done by giving -'git-merge-one-file' command as one of the arguments to -'git-merge-index' command: +'git merge-one-file' command as one of the arguments to +'git merge-index' command: ------------ $ git merge-index git-merge-one-file hello @@ -1270,7 +1230,7 @@ ERROR: Merge conflict in hello fatal: merge program failed ------------ -'git-merge-one-file' script is called with parameters to +'git merge-one-file' script is called with parameters to describe those three versions, and is responsible to leave the merge results in the working tree. It is a fairly straightforward shell script, and @@ -1283,15 +1243,15 @@ the working tree.. This can be seen if you run `ls-files ------------ $ git ls-files --stage 100644 7f8b141b65fdcee47321e399a2598a235a032422 0 example -100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello -100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello +100644 557db03de997c86a4a028e1ebd3a1ceb225be238 1 hello +100644 ba42a2a96e3027f3333e13ede4ccf4498c3ae942 2 hello 100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello ------------ This is the state of the index file and the working file after -'git-merge' returns control back to you, leaving the conflicting +'git merge' returns control back to you, leaving the conflicting merge for you to resolve. Notice that the path `hello` is still -unmerged, and what you see with 'git-diff' at this point is +unmerged, and what you see with 'git diff' at this point is differences since stage 2 (i.e. your version). @@ -1314,7 +1274,7 @@ update the public repository from it. This is often called [NOTE] This public repository could further be mirrored, and that is -how git repositories at `kernel.org` are managed. +how Git repositories at `kernel.org` are managed. Publishing the changes from your local (private) repository to your remote (public) repository requires a write privilege on @@ -1328,12 +1288,12 @@ into it later. Obviously, this repository creation needs to be done only once. [NOTE] -'git-push' uses a pair of programs, -'git-send-pack' on your local machine, and 'git-receive-pack' +'git push' uses a pair of commands, +'git send-pack' on your local machine, and 'git-receive-pack' on the remote machine. The communication between the two over the network internally uses an SSH connection. -Your private repository's git directory is usually `.git`, but +Your private repository's Git directory is usually `.git`, but your public repository is often named after the project name, i.e. `<project>.git`. Let's create such a public repository for project `my-git`. After logging into the remote machine, create @@ -1343,8 +1303,8 @@ an empty directory: $ mkdir my-git.git ------------ -Then, make that directory into a git repository by running -'git-init', but this time, since its name is not the usual +Then, make that directory into a Git repository by running +'git init', but this time, since its name is not the usual `.git`, we do things slightly differently: ------------ @@ -1382,7 +1342,7 @@ This synchronizes your public repository to match the named branch head (i.e. `master` in this case) and objects reachable from them in your current repository. -As a real example, this is how I update my public git +As a real example, this is how I update my public Git repository. Kernel.org mirror network takes care of the propagation to other publicly visible machines: @@ -1395,9 +1355,9 @@ Packing your repository ----------------------- Earlier, we saw that one file under `.git/objects/??/` directory -is stored for each git object you create. This representation +is stored for each Git object you create. This representation is efficient to create atomically and safely, but -not so convenient to transport over the network. Since git objects are +not so convenient to transport over the network. Since Git objects are immutable once they are created, there is a way to optimize the storage by "packing them together". The command @@ -1407,12 +1367,12 @@ $ git repack will do it for you. If you followed the tutorial examples, you would have accumulated about 17 objects in `.git/objects/??/` -directories by now. 'git-repack' tells you how many objects it -packed, and stores the packed file in `.git/objects/pack` +directories by now. 'git repack' tells you how many objects it +packed, and stores the packed file in the `.git/objects/pack` directory. [NOTE] -You will see two files, `pack-\*.pack` and `pack-\*.idx`, +You will see two files, `pack-*.pack` and `pack-*.idx`, in `.git/objects/pack` directory. They are closely related to each other, and if you ever copy them by hand to a different repository for whatever reason, you should make sure you copy @@ -1420,7 +1380,7 @@ them together. The former holds all the data from the objects in the pack, and the latter holds the index for random access. -If you are paranoid, running 'git-verify-pack' command would +If you are paranoid, running 'git verify-pack' command would detect if you have a corrupt pack, but do not worry too much. Our programs are always perfect ;-). @@ -1456,7 +1416,7 @@ while, depending on how active your project is. When a repository is synchronized via `git push` and `git pull` objects packed in the source repository are usually stored -unpacked in the destination, unless rsync transport is used. +unpacked in the destination. While this allows you to use different packing strategies on both ends, it also means you may need to repack both repositories every once in a while. @@ -1465,14 +1425,14 @@ repositories every once in a while. Working with Others ------------------- -Although git is a truly distributed system, it is often +Although Git is a truly distributed system, it is often convenient to organize your project with an informal hierarchy of developers. Linux kernel development is run this way. There is a nice illustration (page 17, "Merges to Mainline") in -link:http://www.xenotime.net/linux/mentor/linux-mentoring-2006.pdf[Randy Dunlap's presentation]. +http://www.xenotime.net/linux/mentor/linux-mentoring-2006.pdf[Randy Dunlap's presentation]. It should be stressed that this hierarchy is purely *informal*. -There is nothing fundamental in git that enforces the "chain of +There is nothing fundamental in Git that enforces the "chain of patch flow" this hierarchy implies. You do not have to pull from only one remote repository. @@ -1487,17 +1447,17 @@ If other people are pulling from your repository over dumb transport protocols (HTTP), you need to keep this repository 'dumb transport friendly'. After `git init`, `$GIT_DIR/hooks/post-update.sample` copied from the standard templates -would contain a call to 'git-update-server-info' +would contain a call to 'git update-server-info' but you need to manually enable the hook with `mv post-update.sample post-update`. This makes sure -'git-update-server-info' keeps the necessary files up-to-date. +'git update-server-info' keeps the necessary files up-to-date. 3. Push into the public repository from your primary repository. -4. 'git-repack' the public repository. This establishes a big +4. 'git repack' the public repository. This establishes a big pack that contains the initial set of objects as the - baseline, and possibly 'git-prune' if the transport + baseline, and possibly 'git prune' if the transport used for pulling from your repository supports packed repositories. @@ -1511,14 +1471,14 @@ You can repack this private repository whenever you feel like. 6. Push your changes to the public repository, and announce it to the public. -7. Every once in a while, 'git-repack' the public repository. +7. Every once in a while, 'git repack' the public repository. Go back to step 5. and continue working. A recommended work cycle for a "subsystem maintainer" who works on that project and has an own "public repository" goes like this: -1. Prepare your work repository, by 'git-clone' the public +1. Prepare your work repository, by running 'git clone' on the public repository of the "project lead". The URL used for the initial cloning is stored in the remote.origin.url configuration variable. @@ -1533,7 +1493,7 @@ on that project and has an own "public repository" goes like this: point at the repository you are borrowing from. 4. Push into the public repository from your primary - repository. Run 'git-repack', and possibly 'git-prune' if the + repository. Run 'git repack', and possibly 'git prune' if the transport used for pulling from your repository supports packed repositories. @@ -1550,7 +1510,7 @@ like. "project lead" and possibly your "sub-subsystem maintainers" to pull from it. -7. Every once in a while, 'git-repack' the public repository. +7. Every once in a while, 'git repack' the public repository. Go back to step 5. and continue working. @@ -1558,7 +1518,7 @@ A recommended work cycle for an "individual developer" who does not have a "public" repository is somewhat different. It goes like this: -1. Prepare your work repository, by 'git-clone' the public +1. Prepare your work repository, by 'git clone' the public repository of the "project lead" (or a "subsystem maintainer", if you work on a subsystem). The URL used for the initial cloning is stored in the remote.origin.url @@ -1583,9 +1543,9 @@ like this: Working with Others, Shared Repository Style -------------------------------------------- -If you are coming from CVS background, the style of cooperation +If you are coming from a CVS background, the style of cooperation suggested in the previous section may be new to you. You do not -have to worry. git supports "shared public repository" style of +have to worry. Git supports the "shared public repository" style of cooperation you are probably more familiar with as well. See linkgit:gitcvs-migration[7] for the details. @@ -1595,7 +1555,7 @@ Bundling your work together It is likely that you will be working on more than one thing at a time. It is easy to manage those more-or-less independent tasks -using branches with git. +using branches with Git. We have already seen how branches work previously, with "fun and work" example using two branches. The idea is the @@ -1656,8 +1616,8 @@ $ git reset --hard master~2 ------------ You can make sure `git show-branch` matches the state before -those two 'git-merge' you just did. Then, instead of running -two 'git-merge' commands in a row, you would merge these two +those two 'git merge' you just did. Then, instead of running +two 'git merge' commands in a row, you would merge these two branch heads (this is known as 'making an Octopus'): ------------ @@ -1675,7 +1635,7 @@ $ git show-branch ++* [master~2] Pretty-print messages. ------------ -Note that you should not do Octopus because you can. An octopus +Note that you should not do Octopus just because you can. An octopus is a valid thing to do and often makes it easier to view the commit history if you are merging more than two independent changes at the same time. However, if you have merge conflicts @@ -1693,9 +1653,9 @@ linkgit:gittutorial[7], linkgit:gittutorial-2[7], linkgit:gitcvs-migration[7], linkgit:git-help[1], -link:everyday.html[Everyday git], +linkgit:giteveryday[7], link:user-manual.html[The Git User's Manual] GIT --- -Part of the linkgit:git[1] suite. +Part of the linkgit:git[1] suite |