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diff --git a/Documentation/user-manual.txt b/Documentation/user-manual.txt index c5641af..f13a846 100644 --- a/Documentation/user-manual.txt +++ b/Documentation/user-manual.txt @@ -13,17 +13,27 @@ to build and test a particular version of a software project, search for regressions, and so on. People needing to do actual development will also want to read -<<Developing-with-git>> and <<sharing-development>>. +<<Developing-With-git>> and <<sharing-development>>. Further chapters cover more specialized topics. Comprehensive reference documentation is available through the man -pages. For a command such as "git clone <repo>", just use +pages, or linkgit:git-help[1] command. For example, for the command +"git clone <repo>", you can either use: ------------------------------------------------ $ man git-clone ------------------------------------------------ +or: + +------------------------------------------------ +$ git help clone +------------------------------------------------ + +With the latter, you can use the manual viewer of your choice; see +linkgit:git-help[1] for more information. + See also <<git-quick-start>> for a brief overview of git commands, without any explanation. @@ -49,7 +59,7 @@ project in mind, here are some interesting examples: ------------------------------------------------ # git itself (approx. 10MB download): $ git clone git://git.kernel.org/pub/scm/git/git.git - # the linux kernel (approx. 150MB download): + # the Linux kernel (approx. 150MB download): $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git ------------------------------------------------ @@ -178,7 +188,7 @@ As you can see, a commit shows who made the latest change, what they did, and why. Every commit has a 40-hexdigit id, sometimes called the "object name" or the -"SHA1 id", shown on the first line of the "git-show" output. You can usually +"SHA-1 id", shown on the first line of the "git show" output. You can usually refer to a commit by a shorter name, such as a tag or a branch name, but this longer name can also be useful. Most importantly, it is a globally unique name for this commit: so if you tell somebody else the object name (for @@ -297,7 +307,7 @@ ref: refs/heads/master Examining an old version without creating a new branch ------------------------------------------------------ -The git-checkout command normally expects a branch head, but will also +The `git checkout` command normally expects a branch head, but will also accept an arbitrary commit; for example, you can check out the commit referenced by a tag: @@ -310,7 +320,7 @@ If you want to create a new branch from this checkout, you may do so HEAD is now at 427abfa... Linux v2.6.17 ------------------------------------------------ -The HEAD then refers to the SHA1 of the commit instead of to a branch, +The HEAD then refers to the SHA-1 of the commit instead of to a branch, and git branch shows that you are no longer on a branch: ------------------------------------------------ @@ -334,7 +344,8 @@ Examining branches from a remote repository The "master" branch that was created at the time you cloned is a copy of the HEAD in the repository that you cloned from. That repository may also have had other branches, though, and your local repository -keeps branches which track each of those remote branches, which you +keeps branches which track each of those remote branches, called +remote-tracking branches, which you can view using the "-r" option to linkgit:git-branch[1]: ------------------------------------------------ @@ -349,13 +360,23 @@ $ git branch -r origin/todo ------------------------------------------------ -You cannot check out these remote-tracking branches, but you can -examine them on a branch of your own, just as you would a tag: +In this example, "origin" is called a remote repository, or "remote" +for short. The branches of this repository are called "remote +branches" from our point of view. The remote-tracking branches listed +above were created based on the remote branches at clone time and will +be updated by "git fetch" (hence "git pull") and "git push". See +<<Updating-a-repository-With-git-fetch>> for details. + +You might want to build on one of these remote-tracking branches +on a branch of your own, just as you would for a tag: ------------------------------------------------ $ git checkout -b my-todo-copy origin/todo ------------------------------------------------ +You can also check out "origin/todo" directly to examine it or +write a one-off patch. See <<detached-head,detached head>>. + Note that the name "origin" is just the name that git uses by default to refer to the repository that you cloned from. @@ -387,10 +408,10 @@ is usually a shortcut for the HEAD branch in the repository "origin". For the complete list of paths which git checks for references, and the order it uses to decide which to choose when there are multiple references with the same shorthand name, see the "SPECIFYING -REVISIONS" section of linkgit:git-rev-parse[1]. +REVISIONS" section of linkgit:gitrevisions[7]. -[[Updating-a-repository-with-git-fetch]] -Updating a repository with git-fetch +[[Updating-a-repository-With-git-fetch]] +Updating a repository with git fetch ------------------------------------ Eventually the developer cloned from will do additional work in her @@ -417,7 +438,7 @@ $ git fetch linux-nfs ------------------------------------------------- New remote-tracking branches will be stored under the shorthand name -that you gave "git-remote add", in this case linux-nfs: +that you gave "git remote add", in this case linux-nfs: ------------------------------------------------- $ git branch -r @@ -425,7 +446,7 @@ linux-nfs/master origin/master ------------------------------------------------- -If you run "git fetch <remote>" later, the tracking branches for the +If you run "git fetch <remote>" later, the remote-tracking branches for the named <remote> will be updated. If you examine the file .git/config, you will see that git has added @@ -479,10 +500,10 @@ Bisecting: 3537 revisions left to test after this ------------------------------------------------- If you run "git branch" at this point, you'll see that git has -temporarily moved you to a new branch named "bisect". This branch -points to a commit (with commit id 65934...) that is reachable from -"master" but not from v2.6.18. Compile and test it, and see whether -it crashes. Assume it does crash. Then: +temporarily moved you in "(no branch)". HEAD is now detached from any +branch and points directly to a commit (with commit id 65934...) that +is reachable from "master" but not from v2.6.18. Compile and test it, +and see whether it crashes. Assume it does crash. Then: ------------------------------------------------- $ git bisect bad @@ -504,10 +525,9 @@ report with the commit id. Finally, run $ git bisect reset ------------------------------------------------- -to return you to the branch you were on before and delete the -temporary "bisect" branch. +to return you to the branch you were on before. -Note that the version which git-bisect checks out for you at each +Note that the version which `git bisect` checks out for you at each point is just a suggestion, and you're free to try a different version if you think it would be a good idea. For example, occasionally you may land on a commit that broke something unrelated; @@ -528,6 +548,22 @@ $ git reset --hard fb47ddb2db... then test, run "bisect good" or "bisect bad" as appropriate, and continue. +Instead of "git bisect visualize" and then "git reset --hard +fb47ddb2db...", you might just want to tell git that you want to skip +the current commit: + +------------------------------------------------- +$ git bisect skip +------------------------------------------------- + +In this case, though, git may not eventually be able to tell the first +bad one between some first skipped commits and a later bad commit. + +There are also ways to automate the bisecting process if you have a +test script that can tell a good from a bad commit. See +linkgit:git-bisect[1] for more information about this and other "git +bisect" features. + [[naming-commits]] Naming commits -------------- @@ -543,7 +579,7 @@ We have seen several ways of naming commits already: - HEAD: refers to the head of the current branch There are many more; see the "SPECIFYING REVISIONS" section of the -linkgit:git-rev-parse[1] man page for the complete list of ways to +linkgit:gitrevisions[7] man page for the complete list of ways to name revisions. Some examples: ------------------------------------------------- @@ -567,11 +603,11 @@ In addition to HEAD, there are several other special names for commits: Merges (to be discussed later), as well as operations such as -git-reset, which change the currently checked-out commit, generally +`git reset`, which change the currently checked-out commit, generally set ORIG_HEAD to the value HEAD had before the current operation. -The git-fetch operation always stores the head of the last fetched -branch in FETCH_HEAD. For example, if you run git fetch without +The `git fetch` operation always stores the head of the last fetched +branch in FETCH_HEAD. For example, if you run `git fetch` without specifying a local branch as the target of the operation ------------------------------------------------- @@ -714,7 +750,7 @@ $ git log --pretty=oneline origin..mybranch | wc -l ------------------------------------------------- Alternatively, you may often see this sort of thing done with the -lower-level command linkgit:git-rev-list[1], which just lists the SHA1's +lower-level command linkgit:git-rev-list[1], which just lists the SHA-1's of all the given commits: ------------------------------------------------- @@ -884,7 +920,7 @@ commits reachable from some head but not from any tag in the repository: $ gitk $( git show-ref --heads ) --not $( git show-ref --tags ) ------------------------------------------------- -(See linkgit:git-rev-parse[1] for explanations of commit-selecting +(See linkgit:gitrevisions[7] for explanations of commit-selecting syntax such as `--not`.) [[making-a-release]] @@ -930,7 +966,7 @@ echo "git diff --stat --summary -M v$last v$new > ../diffstat-$new" and then he just cut-and-pastes the output commands after verifying that they look OK. -[[Finding-comments-with-given-content]] +[[Finding-commits-With-given-Content]] Finding commits referencing a file with given content ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -947,7 +983,7 @@ Figuring out why this works is left as an exercise to the (advanced) student. The linkgit:git-log[1], linkgit:git-diff-tree[1], and linkgit:git-hash-object[1] man pages may prove helpful. -[[Developing-with-git]] +[[Developing-With-git]] Developing with git =================== @@ -984,7 +1020,7 @@ $ git init If you have some initial content (say, a tarball): ------------------------------------------------- -$ tar -xzvf project.tar.gz +$ tar xzvf project.tar.gz $ cd project $ git init $ git add . # include everything below ./ in the first commit: @@ -1048,9 +1084,9 @@ $ git diff shows the difference between the working tree and the index file. -Note that "git-add" always adds just the current contents of a file +Note that "git add" always adds just the current contents of a file to the index; further changes to the same file will be ignored unless -you run git-add on the file again. +you run `git add` on the file again. When you're ready, just run @@ -1111,10 +1147,10 @@ Ignoring files A project will often generate files that you do 'not' want to track with git. This typically includes files generated by a build process or temporary backup files made by your editor. Of course, 'not' tracking files with git -is just a matter of 'not' calling "`git-add`" on them. But it quickly becomes +is just a matter of 'not' calling `git add` on them. But it quickly becomes annoying to have these untracked files lying around; e.g. they make -"`git add .`" and "`git commit -a`" practically useless, and they keep -showing up in the output of "`git status`". +`git add .` practically useless, and they keep showing up in the output of +`git status`. You can tell git to ignore certain files by creating a file called .gitignore in the top level of your working directory, with contents such as: @@ -1158,7 +1194,23 @@ $ git merge branchname ------------------------------------------------- merges the development in the branch "branchname" into the current -branch. If there are conflicts--for example, if the same file is +branch. + +A merge is made by combining the changes made in "branchname" and the +changes made up to the latest commit in your current branch since +their histories forked. The work tree is overwritten by the result of +the merge when this combining is done cleanly, or overwritten by a +half-merged results when this combining results in conflicts. +Therefore, if you have uncommitted changes touching the same files as +the ones impacted by the merge, Git will refuse to proceed. Most of +the time, you will want to commit your changes before you can merge, +and if you don't, then linkgit:git-stash[1] can take these changes +away while you're doing the merge, and reapply them afterwards. + +If the changes are independent enough, Git will automatically complete +the merge and commit the result (or reuse an existing commit in case +of <<fast-forwards,fast-forward>>, see below). On the other hand, +if there are conflicts--for example, if the same file is modified in two different ways in the remote branch and the local branch--then you are warned; the output may look something like this: @@ -1315,7 +1367,7 @@ These will display all commits which exist only on HEAD or on MERGE_HEAD, and which touch an unmerged file. You may also use linkgit:git-mergetool[1], which lets you merge the -unmerged files using external tools such as emacs or kdiff3. +unmerged files using external tools such as Emacs or kdiff3. Each time you resolve the conflicts in a file and update the index: @@ -1324,7 +1376,7 @@ $ git add file.txt ------------------------------------------------- the different stages of that file will be "collapsed", after which -git-diff will (by default) no longer show diffs for that file. +`git diff` will (by default) no longer show diffs for that file. [[undoing-a-merge]] Undoing a merge @@ -1359,7 +1411,7 @@ were merged. However, if the current branch is a descendant of the other--so every commit present in the one is already contained in the other--then git -just performs a "fast forward"; the head of the current branch is moved +just performs a "fast-forward"; the head of the current branch is moved forward to point at the head of the merged-in branch, without any new commits being created. @@ -1421,7 +1473,7 @@ Fixing a mistake by rewriting history If the problematic commit is the most recent commit, and you have not yet made that commit public, then you may just -<<undoing-a-merge,destroy it using git-reset>>. +<<undoing-a-merge,destroy it using `git reset`>>. Alternatively, you can edit the working directory and update the index to fix your @@ -1449,7 +1501,7 @@ Checking out an old version of a file In the process of undoing a previous bad change, you may find it useful to check out an older version of a particular file using -linkgit:git-checkout[1]. We've used git-checkout before to switch +linkgit:git-checkout[1]. We've used `git checkout` before to switch branches, but it has quite different behavior if it is given a path name: the command @@ -1482,7 +1534,7 @@ so on a different branch and then coming back), unstash the work-in-progress changes. ------------------------------------------------ -$ git stash "work in progress for foo feature" +$ git stash save "work in progress for foo feature" ------------------------------------------------ This command will save your changes away to the `stash`, and @@ -1495,10 +1547,10 @@ $ git commit -a -m "blorpl: typofix" ------------------------------------------------ After that, you can go back to what you were working on with -`git stash apply`: +`git stash pop`: ------------------------------------------------ -$ git stash apply +$ git stash pop ------------------------------------------------ @@ -1517,7 +1569,7 @@ $ git gc ------------------------------------------------- to recompress the archive. This can be very time-consuming, so -you may prefer to run git-gc when you are not doing other work. +you may prefer to run `git gc` when you are not doing other work. [[ensuring-reliability]] @@ -1594,7 +1646,7 @@ you've checked out. The reflogs are kept by default for 30 days, after which they may be pruned. See linkgit:git-reflog[1] and linkgit:git-gc[1] to learn how to control this pruning, and see the "SPECIFYING REVISIONS" -section of linkgit:git-rev-parse[1] for details. +section of linkgit:gitrevisions[7] for details. Note that the reflog history is very different from normal git history. While normal history is shared by every repository that works on the @@ -1609,7 +1661,7 @@ In some situations the reflog may not be able to save you. For example, suppose you delete a branch, then realize you need the history it contained. The reflog is also deleted; however, if you have not yet pruned the repository, then you may still be able to find the lost -commits in the dangling objects that git-fsck reports. See +commits in the dangling objects that `git fsck` reports. See <<dangling-objects>> for the details. ------------------------------------------------- @@ -1650,16 +1702,16 @@ dangling objects can arise in other situations. Sharing development with others =============================== -[[getting-updates-with-git-pull]] -Getting updates with git-pull +[[getting-updates-With-git-pull]] +Getting updates with git pull ----------------------------- -After you clone a repository and make a few changes of your own, you +After you clone a repository and commit a few changes of your own, you may wish to check the original repository for updates and merge them into your own work. -We have already seen <<Updating-a-repository-with-git-fetch,how to -keep remote tracking branches up to date>> with linkgit:git-fetch[1], +We have already seen <<Updating-a-repository-With-git-fetch,how to +keep remote-tracking branches up to date>> with linkgit:git-fetch[1], and how to merge two branches. So you can merge in changes from the original repository's master branch with: @@ -1675,15 +1727,21 @@ one step: $ git pull origin master ------------------------------------------------- -In fact, if you have "master" checked out, then by default "git pull" -merges from the HEAD branch of the origin repository. So often you can +In fact, if you have "master" checked out, then this branch has been +configured by "git clone" to get changes from the HEAD branch of the +origin repository. So often you can accomplish the above with just a simple ------------------------------------------------- $ git pull ------------------------------------------------- -More generally, a branch that is created from a remote branch will pull +This command will fetch changes from the remote branches to your +remote-tracking branches `origin/*`, and merge the default branch into +the current branch. + +More generally, a branch that is created from a remote-tracking branch +will pull by default from that branch. See the descriptions of the branch.<name>.remote and branch.<name>.merge options in linkgit:git-config[1], and the discussion of the `--track` option in @@ -1694,10 +1752,10 @@ producing a default commit message documenting the branch and repository that you pulled from. (But note that no such commit will be created in the case of a -<<fast-forwards,fast forward>>; instead, your branch will just be +<<fast-forwards,fast-forward>>; instead, your branch will just be updated to point to the latest commit from the upstream branch.) -The git-pull command can also be given "." as the "remote" repository, +The `git pull` command can also be given "." as the "remote" repository, in which case it just merges in a branch from the current repository; so the commands @@ -1769,8 +1827,8 @@ Public git repositories Another way to submit changes to a project is to tell the maintainer of that project to pull the changes from your repository using -linkgit:git-pull[1]. In the section "<<getting-updates-with-git-pull, -Getting updates with git-pull>>" we described this as a way to get +linkgit:git-pull[1]. In the section "<<getting-updates-With-git-pull, +Getting updates with `git pull`>>" we described this as a way to get updates from the "main" repository, but it works just as well in the other direction. @@ -1822,7 +1880,7 @@ Setting up a public repository ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Assume your personal repository is in the directory ~/proj. We -first create a new clone of the repository and tell git-daemon that it +first create a new clone of the repository and tell `git daemon` that it is meant to be public: ------------------------------------------------- @@ -1853,10 +1911,10 @@ repository>>", below. Otherwise, all you need to do is start linkgit:git-daemon[1]; it will listen on port 9418. By default, it will allow access to any directory that looks like a git directory and contains the magic file -git-daemon-export-ok. Passing some directory paths as git-daemon +git-daemon-export-ok. Passing some directory paths as `git daemon` arguments will further restrict the exports to those paths. -You can also run git-daemon as an inetd service; see the +You can also run `git daemon` as an inetd service; see the linkgit:git-daemon[1] man page for details. (See especially the examples section.) @@ -1875,7 +1933,7 @@ adjustments to give web clients some extra information they need: $ mv proj.git /home/you/public_html/proj.git $ cd proj.git $ git --bare update-server-info -$ chmod a+x hooks/post-update +$ mv hooks/post-update.sample hooks/post-update ------------------------------------------------- (For an explanation of the last two lines, see @@ -1917,8 +1975,8 @@ or just $ git push ssh://yourserver.com/~you/proj.git master ------------------------------------------------- -As with git-fetch, git-push will complain if this does not result in a -<<fast-forwards,fast forward>>; see the following section for details on +As with `git fetch`, `git push` will complain if this does not result in a +<<fast-forwards,fast-forward>>; see the following section for details on handling this case. Note that the target of a "push" is normally a @@ -1927,7 +1985,7 @@ repository that has a checked-out working tree, but the working tree will not be updated by the push. This may lead to unexpected results if the branch you push to is the currently checked-out branch! -As with git-fetch, you may also set up configuration options to +As with `git fetch`, you may also set up configuration options to save typing; so, for example, after ------------------------------------------------- @@ -1951,7 +2009,7 @@ details. What to do when a push fails ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -If a push would not result in a <<fast-forwards,fast forward>> of the +If a push would not result in a <<fast-forwards,fast-forward>> of the remote branch, then it will fail with an error like: ------------------------------------------------- @@ -1963,13 +2021,13 @@ error: failed to push to 'ssh://yourserver.com/~you/proj.git' This can happen, for example, if you: - - use `git-reset --hard` to remove already-published commits, or - - use `git-commit --amend` to replace already-published commits + - use `git reset --hard` to remove already-published commits, or + - use `git commit --amend` to replace already-published commits (as in <<fixing-a-mistake-by-rewriting-history>>), or - - use `git-rebase` to rebase any already-published commits (as + - use `git rebase` to rebase any already-published commits (as in <<using-git-rebase>>). -You may force git-push to perform the update anyway by preceding the +You may force `git push` to perform the update anyway by preceding the branch name with a plus sign: ------------------------------------------------- @@ -1979,7 +2037,7 @@ $ git push ssh://yourserver.com/~you/proj.git +master Normally whenever a branch head in a public repository is modified, it is modified to point to a descendant of the commit that it pointed to before. By forcing a push in this situation, you break that convention. -(See <<problems-with-rewriting-history>>.) +(See <<problems-With-rewriting-history>>.) Nevertheless, this is a common practice for people that need a simple way to publish a work-in-progress patch series, and it is an acceptable @@ -2011,7 +2069,7 @@ advantages over the central shared repository: - Git's ability to quickly import and merge patches allows a single maintainer to process incoming changes even at very - high rates. And when that becomes too much, git-pull provides + high rates. And when that becomes too much, `git pull` provides an easy way for that maintainer to delegate this job to other maintainers while still allowing optional review of incoming changes. @@ -2065,7 +2123,7 @@ $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git $ cd work ------------------------------------------------- -Linus's tree will be stored in the remote branch named origin/master, +Linus's tree will be stored in the remote-tracking branch named origin/master, and can be updated using linkgit:git-fetch[1]; you can track other public trees using linkgit:git-remote[1] to set up a "remote" and linkgit:git-fetch[1] to keep them up-to-date; see @@ -2090,7 +2148,7 @@ $ git checkout release && git pull Important note! If you have any local changes in these branches, then this merge will create a commit object in the history (with no local -changes git will simply do a "Fast forward" merge). Many people dislike +changes git will simply do a "fast-forward" merge). Many people dislike the "noise" that this creates in the Linux history, so you should avoid doing this capriciously in the "release" branch, as these noisy commits will become part of the permanent history when you ask Linus to pull @@ -2130,11 +2188,14 @@ $ git push mytree release Now to apply some patches from the community. Think of a short snappy name for a branch to hold this patch (or related group of -patches), and create a new branch from the current tip of Linus's -branch: +patches), and create a new branch from a recent stable tag of +Linus's branch. Picking a stable base for your branch will: +1) help you: by avoiding inclusion of unrelated and perhaps lightly +tested changes +2) help future bug hunters that use "git bisect" to find problems ------------------------------------------------- -$ git checkout -b speed-up-spinlocks origin +$ git checkout -b speed-up-spinlocks v2.6.35 ------------------------------------------------- Now you apply the patch(es), run some tests, and commit the change(s). If @@ -2379,7 +2440,7 @@ use them, and then explain some of the problems that can arise because you are rewriting history. [[using-git-rebase]] -Keeping a patch series up to date using git-rebase +Keeping a patch series up to date using git rebase -------------------------------------------------- Suppose that you create a branch "mywork" on a remote-tracking branch @@ -2398,9 +2459,9 @@ You have performed no merges into mywork, so it is just a simple linear sequence of patches on top of "origin": ................................................ - o--o--o <-- origin + o--o--O <-- origin \ - o--o--o <-- mywork + a--b--c <-- mywork ................................................ Some more interesting work has been done in the upstream project, and @@ -2443,9 +2504,9 @@ patches to the new mywork. The result will look like: ................................................ In the process, it may discover conflicts. In that case it will stop -and allow you to fix the conflicts; after fixing conflicts, use "git-add" +and allow you to fix the conflicts; after fixing conflicts, use `git add` to update the index with those contents, and then, instead of -running git-commit, just run +running `git commit`, just run ------------------------------------------------- $ git rebase --continue @@ -2483,7 +2544,7 @@ with $ git tag bad mywork~5 ------------------------------------------------- -(Either gitk or git-log may be useful for finding the commit.) +(Either gitk or `git log` may be useful for finding the commit.) Then check out that commit, edit it, and rebase the rest of the series on top of it (note that we could check out the commit on a temporary @@ -2524,12 +2585,12 @@ $ gitk origin..mywork & and browse through the list of patches in the mywork branch using gitk, applying them (possibly in a different order) to mywork-new using -cherry-pick, and possibly modifying them as you go using `commit --amend`. +cherry-pick, and possibly modifying them as you go using `git commit --amend`. The linkgit:git-gui[1] command may also help as it allows you to individually select diff hunks for inclusion in the index (by right-clicking on the diff hunk and choosing "Stage Hunk for Commit"). -Another technique is to use git-format-patch to create a series of +Another technique is to use `git format-patch` to create a series of patches, then reset the state to before the patches: ------------------------------------------------- @@ -2544,11 +2605,11 @@ them again with linkgit:git-am[1]. Other tools ----------- -There are numerous other tools, such as StGIT, which exist for the +There are numerous other tools, such as StGit, which exist for the purpose of maintaining a patch series. These are outside of the scope of this manual. -[[problems-with-rewriting-history]] +[[problems-With-rewriting-history]] Problems with rewriting history ------------------------------- @@ -2637,7 +2698,7 @@ you know is that D is bad, that Z is good, and that linkgit:git-bisect[1] identifies C as the culprit, how will you figure out that the problem is due to this change in semantics? -When the result of a git-bisect is a non-merge commit, you should +When the result of a `git bisect` is a non-merge commit, you should normally be able to discover the problem by examining just that commit. Developers can make this easy by breaking their changes into small self-contained commits. That won't help in the case above, however, @@ -2700,13 +2761,13 @@ master branch. In more detail: git fetch and fast-forwards --------------------------- -In the previous example, when updating an existing branch, "git-fetch" +In the previous example, when updating an existing branch, "git fetch" checks to make sure that the most recent commit on the remote branch is a descendant of the most recent commit on your copy of the branch before updating your copy of the branch to point at the new -commit. Git calls this process a <<fast-forwards,fast forward>>. +commit. Git calls this process a <<fast-forwards,fast-forward>>. -A fast forward looks something like this: +A fast-forward looks something like this: ................................................ o--o--o--o <-- old head of the branch @@ -2726,7 +2787,7 @@ resulting in a situation like: o--o--o <-- new head of the branch ................................................ -In this case, "git-fetch" will fail, and print out a warning. +In this case, "git fetch" will fail, and print out a warning. In that case, you can still force git to update to the new head, as described in the following section. However, note that in the @@ -2735,7 +2796,7 @@ unless you've already created a reference of your own pointing to them. [[forcing-fetch]] -Forcing git-fetch to do non-fast-forward updates +Forcing git fetch to do non-fast-forward updates ------------------------------------------------ If git fetch fails because the new head of a branch is not a @@ -2756,8 +2817,8 @@ Be aware that commits that the old version of example/master pointed at may be lost, as we saw in the previous section. [[remote-branch-configuration]] -Configuring remote branches ---------------------------- +Configuring remote-tracking branches +------------------------------------ We saw above that "origin" is just a shortcut to refer to the repository that you originally cloned from. This information is @@ -2810,8 +2871,8 @@ You can also add a "+" to force the update each time: $ git config remote.example.fetch +master:ref/remotes/example/master ------------------------------------------------- -Don't do this unless you're sure you won't mind "git-fetch" possibly -throwing away commits on mybranch. +Don't do this unless you're sure you won't mind "git fetch" possibly +throwing away commits on 'example/master'. Also note that all of the above configuration can be performed by directly editing the file .git/config instead of using @@ -2840,8 +2901,8 @@ The Object Database We already saw in <<understanding-commits>> that all commits are stored under a 40-digit "object name". In fact, all the information needed to represent the history of a project is stored in objects with such names. -In each case the name is calculated by taking the SHA1 hash of the -contents of the object. The SHA1 hash is a cryptographic hash function. +In each case the name is calculated by taking the SHA-1 hash of the +contents of the object. The SHA-1 hash is a cryptographic hash function. What that means to us is that it is impossible to find two different objects with the same name. This has a number of advantages; among others: @@ -2852,10 +2913,10 @@ others: same content stored in two repositories will always be stored under the same name. - Git can detect errors when it reads an object, by checking that the - object's name is still the SHA1 hash of its contents. + object's name is still the SHA-1 hash of its contents. (See <<object-details>> for the details of the object formatting and -SHA1 calculation.) +SHA-1 calculation.) There are four different types of objects: "blob", "tree", "commit", and "tag". @@ -2901,9 +2962,9 @@ committer Junio C Hamano <gitster@pobox.com> 1187591163 -0700 As you can see, a commit is defined by: -- a tree: The SHA1 name of a tree object (as defined below), representing +- a tree: The SHA-1 name of a tree object (as defined below), representing the contents of a directory at a certain point in time. -- parent(s): The SHA1 name of some number of commits which represent the +- parent(s): The SHA-1 name of some number of commits which represent the immediately previous step(s) in the history of the project. The example above has one parent; merge commits may have more than one. A commit with no parents is called a "root" commit, and @@ -2952,13 +3013,13 @@ $ git ls-tree fb3a8bdd0ce ------------------------------------------------ As you can see, a tree object contains a list of entries, each with a -mode, object type, SHA1 name, and name, sorted by name. It represents +mode, object type, SHA-1 name, and name, sorted by name. It represents the contents of a single directory tree. The object type may be a blob, representing the contents of a file, or another tree, representing the contents of a subdirectory. Since trees -and blobs, like all other objects, are named by the SHA1 hash of their -contents, two trees have the same SHA1 name if and only if their +and blobs, like all other objects, are named by the SHA-1 hash of their +contents, two trees have the same SHA-1 name if and only if their contents (including, recursively, the contents of all subdirectories) are identical. This allows git to quickly determine the differences between two related tree objects, since it can ignore any entries with @@ -3004,15 +3065,15 @@ currently checked out. Trust ~~~~~ -If you receive the SHA1 name of a blob from one source, and its contents +If you receive the SHA-1 name of a blob from one source, and its contents from another (possibly untrusted) source, you can still trust that those -contents are correct as long as the SHA1 name agrees. This is because -the SHA1 is designed so that it is infeasible to find different contents +contents are correct as long as the SHA-1 name agrees. This is because +the SHA-1 is designed so that it is infeasible to find different contents that produce the same hash. -Similarly, you need only trust the SHA1 name of a top-level tree object +Similarly, you need only trust the SHA-1 name of a top-level tree object to trust the contents of the entire directory that it refers to, and if -you receive the SHA1 name of a commit from a trusted source, then you +you receive the SHA-1 name of a commit from a trusted source, then you can easily verify the entire history of commits reachable through parents of that commit, and all of those contents of the trees referred to by those commits. @@ -3024,7 +3085,7 @@ that you trust that commit, and the immutability of the history of commits tells others that they can trust the whole history. In other words, you can easily validate a whole archive by just -sending out a single email that tells the people the name (SHA1 hash) +sending out a single email that tells the people the name (SHA-1 hash) of the top commit, and digitally sign that email using something like GPG/PGP. @@ -3065,7 +3126,7 @@ How git stores objects efficiently: pack files ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Newly created objects are initially created in a file named after the -object's SHA1 hash (stored in .git/objects). +object's SHA-1 hash (stored in .git/objects). Unfortunately this system becomes inefficient once a project has a lot of objects. Try this on an old project: @@ -3106,7 +3167,7 @@ $ git prune to remove any of the "loose" objects that are now contained in the pack. This will also remove any unreferenced objects (which may be -created when, for example, you use "git-reset" to remove a commit). +created when, for example, you use "git reset" to remove a commit). You can verify that the loose objects are gone by looking at the .git/objects directory or by running @@ -3135,7 +3196,7 @@ branch still exists, as does everything it pointed to. The branch pointer itself just doesn't, since you replaced it with another one. There are also other situations that cause dangling objects. For -example, a "dangling blob" may arise because you did a "git-add" of a +example, a "dangling blob" may arise because you did a "git add" of a file, but then, before you actually committed it and made it part of the bigger picture, you changed something else in that file and committed that *updated* thing--the old state that you added originally ends up @@ -3185,7 +3246,7 @@ Usually, dangling blobs and trees aren't very interesting. They're almost always the result of either being a half-way mergebase (the blob will often even have the conflict markers from a merge in it, if you have had conflicting merges that you fixed up by hand), or simply -because you interrupted a "git-fetch" with ^C or something like that, +because you interrupted a "git fetch" with ^C or something like that, leaving _some_ of the new objects in the object database, but just dangling and useless. @@ -3200,9 +3261,9 @@ and they'll be gone. But you should only run "git prune" on a quiescent repository--it's kind of like doing a filesystem fsck recovery: you don't want to do that while the filesystem is mounted. -(The same is true of "git-fsck" itself, btw, but since -git-fsck never actually *changes* the repository, it just reports -on what it found, git-fsck itself is never "dangerous" to run. +(The same is true of "git fsck" itself, btw, but since +`git fsck` never actually *changes* the repository, it just reports +on what it found, `git fsck` itself is never 'dangerous' to run. Running it while somebody is actually changing the repository can cause confusing and scary messages, but it won't actually do anything bad. In contrast, running "git prune" while somebody is actively changing the @@ -3272,7 +3333,7 @@ $ git hash-object -w somedirectory/myfile ------------------------------------------------ which will create and store a blob object with the contents of -somedirectory/myfile, and output the sha1 of that object. if you're +somedirectory/myfile, and output the SHA-1 of that object. if you're extremely lucky it might be 4b9458b3786228369c63936db65827de3cc06200, in which case you've guessed right, and the corruption is fixed! @@ -3334,7 +3395,7 @@ The index ----------- The index is a binary file (generally kept in .git/index) containing a -sorted list of path names, each with permissions and the SHA1 of a blob +sorted list of path names, each with permissions and the SHA-1 of a blob object; linkgit:git-ls-files[1] can show you the contents of the index: ------------------------------------------------- @@ -3458,23 +3519,23 @@ $ cd super $ git init $ for i in a b c d do - git submodule add ~/git/$i + git submodule add ~/git/$i $i done ------------------------------------------------- NOTE: Do not use local URLs here if you plan to publish your superproject! -See what files `git-submodule` created: +See what files `git submodule` created: ------------------------------------------------- $ ls -a . .. .git .gitmodules a b c d ------------------------------------------------- -The `git-submodule add` command does a couple of things: +The `git submodule add <repo> <path>` command does a couple of things: -- It clones the submodule under the current directory and by default checks out - the master branch. +- It clones the submodule from <repo> to the given <path> under the + current directory and by default checks out the master branch. - It adds the submodule's clone path to the linkgit:gitmodules[5] file and adds this file to the index, ready to be committed. - It adds the submodule's current commit ID to the index, ready to be @@ -3517,7 +3578,7 @@ init` to add the submodule repository URLs to `.git/config`: $ git submodule init ------------------------------------------------- -Now use `git-submodule update` to clone the repositories and check out the +Now use `git submodule update` to clone the repositories and check out the commits specified in the superproject: ------------------------------------------------- @@ -3527,8 +3588,8 @@ $ ls -a . .. .git a.txt ------------------------------------------------- -One major difference between `git-submodule update` and `git-submodule add` is -that `git-submodule update` checks out a specific commit, rather than the tip +One major difference between `git submodule update` and `git submodule add` is +that `git submodule update` checks out a specific commit, rather than the tip of a branch. It's like checking out a tag: the head is detached, so you're not working on a branch. @@ -3599,6 +3660,26 @@ Did you forget to 'git add'? Unable to checkout '261dfac35cb99d380eb966e102c1197139f7fa24' in submodule path 'a' ------------------------------------------------- +In older git versions it could be easily forgotten to commit new or modified +files in a submodule, which silently leads to similar problems as not pushing +the submodule changes. Starting with git 1.7.0 both "git status" and "git diff" +in the superproject show submodules as modified when they contain new or +modified files to protect against accidentally committing such a state. "git +diff" will also add a "-dirty" to the work tree side when generating patch +output or used with the --submodule option: + +------------------------------------------------- +$ git diff +diff --git a/sub b/sub +--- a/sub ++++ b/sub +@@ -1 +1 @@ +-Subproject commit 3f356705649b5d566d97ff843cf193359229a453 ++Subproject commit 3f356705649b5d566d97ff843cf193359229a453-dirty +$ git diff --submodule +Submodule sub 3f35670..3f35670-dirty: +------------------------------------------------- + You also should not rewind branches in a submodule beyond commits that were ever recorded in any superproject. @@ -3729,7 +3810,7 @@ unsaved state that you might want to restore later!) your current index. Normal operation is just ------------------------------------------------- -$ git read-tree <sha1 of tree> +$ git read-tree <SHA-1 of tree> ------------------------------------------------- and your index file will now be equivalent to the tree that you saved @@ -3744,7 +3825,7 @@ You update your working directory from the index by "checking out" files. This is not a very common operation, since normally you'd just keep your files updated, and rather than write to your working directory, you'd tell the index files about the changes in your -working directory (i.e. `git-update-index`). +working directory (i.e. `git update-index`). However, if you decide to jump to a new version, or check out somebody else's version, or just restore a previous tree, you'd populate your @@ -3757,7 +3838,7 @@ $ git checkout-index filename or, if you want to check out all of the index, use `-a`. -NOTE! git-checkout-index normally refuses to overwrite old files, so +NOTE! `git checkout-index` normally refuses to overwrite old files, so if you have an old version of the tree already checked out, you will need to use the "-f" flag ('before' the "-a" flag or the filename) to 'force' the checkout. @@ -3789,13 +3870,13 @@ You create a commit object by giving it the tree that describes the state at the time of the commit, and a list of parents: ------------------------------------------------- -$ git commit-tree <tree> -p <parent> [-p <parent2> ..] +$ git commit-tree <tree> -p <parent> [(-p <parent2>)...] ------------------------------------------------- and then giving the reason for the commit on stdin (either through redirection from a pipe or file, or by just typing it at the tty). -git-commit-tree will return the name of the object that represents +`git commit-tree` will return the name of the object that represents that commit, and you should save it away for later use. Normally, you'd commit a new `HEAD` state, and while git doesn't care where you save the note about that state, in practice we tend to just write the @@ -3864,7 +3945,7 @@ $ git cat-file blob|tree|commit|tag <objectname> to show its contents. NOTE! Trees have binary content, and as a result there is a special helper for showing that content, called -`git-ls-tree`, which turns the binary content into a more easily +`git ls-tree`, which turns the binary content into a more easily readable form. It's especially instructive to look at "commit" objects, since those @@ -3953,13 +4034,13 @@ $ git ls-files --unmerged ------------------------------------------------ Each line of the `git ls-files --unmerged` output begins with -the blob mode bits, blob SHA1, 'stage number', and the +the blob mode bits, blob SHA-1, 'stage number', and the filename. The 'stage number' is git's way to say which tree it came from: stage 1 corresponds to `$orig` tree, stage 2 `HEAD` tree, and stage3 `$target` tree. Earlier we said that trivial merges are done inside -`git-read-tree -m`. For example, if the file did not change +`git read-tree -m`. For example, if the file did not change from `$orig` to `HEAD` nor `$target`, or if the file changed from `$orig` to `HEAD` and `$orig` to `$target` the same way, obviously the final outcome is what is in `HEAD`. What the @@ -3986,20 +4067,20 @@ $ mv -f hello.c~2 hello.c $ git update-index hello.c ------------------------------------------------- -When a path is in the "unmerged" state, running `git-update-index` for +When a path is in the "unmerged" state, running `git update-index` for that path tells git to mark the path resolved. The above is the description of a git merge at the lowest level, to help you understand what conceptually happens under the hood. -In practice, nobody, not even git itself, runs `git-cat-file` three times -for this. There is a `git-merge-index` program that extracts the +In practice, nobody, not even git itself, runs `git cat-file` three times +for this. There is a `git merge-index` program that extracts the stages to temporary files and calls a "merge" script on it: ------------------------------------------------- $ git merge-index git-merge-one-file hello.c ------------------------------------------------- -and that is what higher level `git-merge -s resolve` is implemented with. +and that is what higher level `git merge -s resolve` is implemented with. [[hacking-git]] Hacking git @@ -4020,12 +4101,12 @@ objects). There are currently four different object types: "blob", Regardless of object type, all objects share the following characteristics: they are all deflated with zlib, and have a header that not only specifies their type, but also provides size information -about the data in the object. It's worth noting that the SHA1 hash +about the data in the object. It's worth noting that the SHA-1 hash that is used to name the object is the hash of the original data plus this header, so `sha1sum` 'file' does not match the object name for 'file'. (Historical note: in the dawn of the age of git the hash -was the sha1 of the 'compressed' object.) +was the SHA-1 of the 'compressed' object.) As a result, the general consistency of an object can always be tested independently of the contents or the type of the object: all objects can @@ -4036,7 +4117,7 @@ size> {plus} <byte\0> {plus} <binary object data>. The structured objects can further have their structure and connectivity to other objects verified. This is generally done with -the `git-fsck` program, which generates a full dependency graph +the `git fsck` program, which generates a full dependency graph of all objects, and verifies their internal consistency (in addition to just verifying their superficial consistency through the hash). @@ -4095,7 +4176,7 @@ functions like `get_sha1_basic()` or the likes. This is just to get you into the groove for the most libified part of Git: the revision walker. -Basically, the initial version of `git-log` was a shell script: +Basically, the initial version of `git log` was a shell script: ---------------------------------------------------------------- $ git-rev-list --pretty $(git-rev-parse --default HEAD "$@") | \ @@ -4104,20 +4185,20 @@ $ git-rev-list --pretty $(git-rev-parse --default HEAD "$@") | \ What does this mean? -`git-rev-list` is the original version of the revision walker, which +`git rev-list` is the original version of the revision walker, which _always_ printed a list of revisions to stdout. It is still functional, -and needs to, since most new Git programs start out as scripts using -`git-rev-list`. +and needs to, since most new Git commands start out as scripts using +`git rev-list`. -`git-rev-parse` is not as important any more; it was only used to filter out +`git rev-parse` is not as important any more; it was only used to filter out options that were relevant for the different plumbing commands that were called by the script. -Most of what `git-rev-list` did is contained in `revision.c` and +Most of what `git rev-list` did is contained in `revision.c` and `revision.h`. It wraps the options in a struct named `rev_info`, which controls how and what revisions are walked, and more. -The original job of `git-rev-parse` is now taken by the function +The original job of `git rev-parse` is now taken by the function `setup_revisions()`, which parses the revisions and the common command line options for the revision walker. This information is stored in the struct `rev_info` for later consumption. You can do your own command line option @@ -4130,7 +4211,7 @@ just have a look at the first implementation of `cmd_log()`; call `git show v1.3.0{tilde}155^2{tilde}4` and scroll down to that function (note that you no longer need to call `setup_pager()` directly). -Nowadays, `git-log` is a builtin, which means that it is _contained_ in the +Nowadays, `git log` is a builtin, which means that it is _contained_ in the command `git`. The source side of a builtin is - a function called `cmd_<bla>`, typically defined in `builtin-<bla>.c`, @@ -4146,7 +4227,7 @@ since they share quite a bit of code. In that case, the commands which are _not_ named like the `.c` file in which they live have to be listed in `BUILT_INS` in the `Makefile`. -`git-log` looks more complicated in C than it does in the original script, +`git log` looks more complicated in C than it does in the original script, but that allows for a much greater flexibility and performance. Here again it is a good point to take a pause. @@ -4157,9 +4238,9 @@ the organization of Git (after you know the basic concepts). So, think about something which you are interested in, say, "how can I access a blob just knowing the object name of it?". The first step is to find a Git command with which you can do it. In this example, it is either -`git-show` or `git-cat-file`. +`git show` or `git cat-file`. -For the sake of clarity, let's stay with `git-cat-file`, because it +For the sake of clarity, let's stay with `git cat-file`, because it - is plumbing, and @@ -4173,7 +4254,7 @@ it does. ------------------------------------------------------------------ git_config(git_default_config); if (argc != 3) - usage("git-cat-file [-t|-s|-e|-p|<type>] <sha1>"); + usage("git cat-file [-t|-s|-e|-p|<type>] <sha1>"); if (get_sha1(argv[2], sha1)) die("Not a valid object name %s", argv[2]); ------------------------------------------------------------------ @@ -4190,9 +4271,9 @@ Two things are interesting here: negative numbers in case of different errors--and 0 on success. - the variable `sha1` in the function signature of `get_sha1()` is `unsigned - char \*`, but is actually expected to be a pointer to `unsigned + char {asterisk}`, but is actually expected to be a pointer to `unsigned char[20]`. This variable will contain the 160-bit SHA-1 of the given - commit. Note that whenever a SHA-1 is passed as `unsigned char \*`, it + commit. Note that whenever a SHA-1 is passed as `unsigned char {asterisk}`, it is the binary representation, as opposed to the ASCII representation in hex characters, which is passed as `char *`. @@ -4218,10 +4299,10 @@ To find out how the result can be used, just read on in `cmd_cat_file()`: ----------------------------------- Sometimes, you do not know where to look for a feature. In many such cases, -it helps to search through the output of `git log`, and then `git-show` the +it helps to search through the output of `git log`, and then `git show` the corresponding commit. -Example: If you know that there was some test case for `git-bundle`, but +Example: If you know that there was some test case for `git bundle`, but do not remember where it was (yes, you _could_ `git grep bundle t/`, but that does not illustrate the point!): @@ -4250,7 +4331,7 @@ You see, Git is actually the best tool to find out about the source of Git itself! [[glossary]] -GIT Glossary +Git Glossary ============ include::glossary-content.txt[] @@ -4341,7 +4422,9 @@ $ git remote show example # get details * remote example URL: git://example.com/project.git Tracked remote branches - master next ... + master + next + ... $ git fetch example # update branches from example $ git branch -r # list all remote branches ----------------------------------------------- @@ -4503,7 +4586,7 @@ The basic requirements: - Whenever possible, section headings should clearly describe the task they explain how to do, in language that requires no more knowledge than necessary: for example, "importing patches into a project" rather - than "the git-am command" + than "the `git am` command" Think about how to create a clear chapter dependency graph that will allow people to get to important topics without necessarily reading @@ -4545,4 +4628,3 @@ Alternates, clone -reference, etc. More on recovery from repository corruption. See: http://marc.theaimsgroup.com/?l=git&m=117263864820799&w=2 http://marc.theaimsgroup.com/?l=git&m=117147855503798&w=2 - http://marc.theaimsgroup.com/?l=git&m=117147855503798&w=2 |