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", 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.
------------------------------------------------
# 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
------------------------------------------------
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
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:
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:
------------------------------------------------
references with the same shorthand name, see the "SPECIFYING
REVISIONS" section of linkgit:git-rev-parse[1].
-[[Updating-a-repository-with-git-fetch]]
+[[Updating-a-repository-With-git-fetch]]
Updating a repository with git fetch
------------------------------------
-------------------------------------------------
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
$ 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;
-------------------------------------------------
which will run gitk and label the commit it chose with a marker that
-says "bisect". Chose a safe-looking commit nearby, note its commit
+says "bisect". Choose a safe-looking commit nearby, note its commit
id, and check it out with:
-------------------------------------------------
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
--------------
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
-------------------------------------------------
-------------------------------------------------
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:
-------------------------------------------------
and then he just cut-and-pastes the output commands after verifying that
they look OK.
-[[Finding-comments-with-given-content]]
+[[Finding-comments-With-given-Content]]
Finding commits referencing a file with given content
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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
===================
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:
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
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:
$ git diff --theirs file.txt # same as the above.
-------------------------------------------------
-The linkgit:git-log[1] and gitk[1] commands also provide special help
+The linkgit:git-log[1] and linkgit:gitk[1] commands also provide special help
for merges:
-------------------------------------------------
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:
-------------------------------------------------
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
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
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
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
-------------------------------------------------
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]]
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.
-------------------------------------------------
Sharing development with others
===============================
-[[getting-updates-with-git-pull]]
+[[getting-updates-With-git-pull]]
Getting updates with git pull
-----------------------------
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
+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:
<<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
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.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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:
-------------------------------------------------
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.)
$ 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
-linkgit:git-update-server-info[1], and the documentation
-linkgit:githooks[5][Hooks used by git].)
+linkgit:git-update-server-info[1] and linkgit:githooks[5].)
Advertise the URL of proj.git. Anybody else should then be able to
clone or pull from that URL, for example with a command line like:
$ git push ssh://yourserver.com/~you/proj.git master
-------------------------------------------------
-As with git-fetch, git-push will complain if this does not result in a
+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.
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
-------------------------------------------------
- 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:
-------------------------------------------------
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
It's also possible for a push to fail in this way when other people have
the right to push to the same repository. In that case, the correct
-solution is to retry the push after first updating your work by either a
-pull or a fetch followed by a rebase; see the
+solution is to retry the push after first updating your work: either by a
+pull, or by a fetch followed by a rebase; see the
<<setting-up-a-shared-repository,next section>> and
-linkgit:gitcvs-migration[7][git for CVS users] for more.
+linkgit:gitcvs-migration[7] for more.
[[setting-up-a-shared-repository]]
Setting up a shared repository
Another way to collaborate is by using a model similar to that
commonly used in CVS, where several developers with special rights
all push to and pull from a single shared repository. See
-linkgit:gitcvs-migration[7][git for CVS users] for instructions on how to
+linkgit:gitcvs-migration[7] for instructions on how to
set this up.
However, while there is nothing wrong with git's support for shared
- 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.
changes are in a specific branch, use:
-------------------------------------------------
-$ git log linux..branchname | git-shortlog
+$ git log linux..branchname | git shortlog
-------------------------------------------------
To see whether it has already been merged into the test or release branches,
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
-------------------------------------------------
This will remove each of your commits from mywork, temporarily saving
-them as patches (in a directory named ".dotest"), update mywork to
+them as patches (in a directory named ".git/rebase-apply"), update mywork to
point at the latest version of origin, then apply each of the saved
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" to update the index with those contents, and then, instead of
-running git-commit, just run
+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
-------------------------------------------------
$ git rebase --continue
$ 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
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:
-------------------------------------------------
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
-------------------------------
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,
git fetch and fast-forwards
---------------------------
-In the previous example, when updating an existing branch, "git
-fetch" checks to make sure that the most recent commit on the remote
+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>>.
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:
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".
- A <<def_blob_object,"blob" object>> is used to store file data.
-- A <<def_tree_object,"tree" object>> is an object that ties one or more
+- A <<def_tree_object,"tree" object>> ties one or more
"blob" objects into a directory structure. In addition, a tree object
can refer to other tree objects, thus creating a directory hierarchy.
- A <<def_commit_object,"commit" object>> ties such directory hierarchies
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
------------------------------------------------
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
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.
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.
A tag object contains an object, object type, tag name, the name of the
person ("tagger") who created the tag, and a message, which may contain
-a signature, as can be seen using the linkgit:git-cat-file[1]:
+a signature, as can be seen using linkgit:git-cat-file[1]:
------------------------------------------------
$ git cat-file tag v1.5.0
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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:
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
Assume the output looks like this:
------------------------------------------------
-$ git-fsck --full
+$ git fsck --full
broken link from tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8
to blob 4b9458b3786228369c63936db65827de3cc06200
missing blob 4b9458b3786228369c63936db65827de3cc06200
------------------------------------------------
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!
-----------
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:
-------------------------------------------------
$ git init
$ for i in a b c d
do
- git submodule add ~/git/$i
+ git submodule add ~/git/$i $i
done
-------------------------------------------------
. .. .git .gitmodules a b c d
-------------------------------------------------
-The `git submodule add` command does a couple of things:
+The `git submodule add <repo> <path>` command does a couple of things:
-- It clones the submodule under the current directory and by default checks out
- the master branch.
+- It clones the submodule from <repo> to the given <path> under the
+ current directory and by default checks out the master branch.
- It adds the submodule's clone path to the linkgit:gitmodules[5] file and
adds this file to the index, ready to be committed.
- It adds the submodule's current commit ID to the index, ready to be
considering a removed file to be a valid thing, and if the file really
does not exist any more, it will update the index accordingly.
-As a special case, you can also do `git-update-index --refresh`, which
+As a special case, you can also do `git update-index --refresh`, which
will refresh the "stat" information of each index to match the current
stat information. It will 'not' update the object status itself, and
it will only update the fields that are used to quickly test whether
index. Normal operation is just
-------------------------------------------------
-$ 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
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
with
-------------------------------------------------
-$ git-checkout-index filename
+$ 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.
Tying it all together
~~~~~~~~~~~~~~~~~~~~~
-To commit a tree you have instantiated with "git-write-tree", you'd
+To commit a tree you have instantiated with "git write-tree", you'd
create a "commit" object that refers to that tree and the history
behind it--most notably the "parent" commits that preceded it in
history.
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
object:
-------------------------------------------------
-$ git-cat-file -t <objectname>
+$ git cat-file -t <objectname>
-------------------------------------------------
shows the type of the object, and once you have the type (which is
usually implicit in where you find the object), you can use
-------------------------------------------------
-$ git-cat-file blob|tree|commit|tag <objectname>
+$ 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
you can do
-------------------------------------------------
-$ git-cat-file commit HEAD
+$ git cat-file commit HEAD
-------------------------------------------------
to see what the top commit was.
of two commits with
-------------------------------------------------
-$ git-merge-base <commit1> <commit2>
+$ git merge-base <commit1> <commit2>
-------------------------------------------------
which will return you the commit they are both based on. You should
do with (for example)
-------------------------------------------------
-$ git-cat-file commit <commitname> | head -1
+$ git cat-file commit <commitname> | head -1
-------------------------------------------------
since the tree object information is always the first line in a commit
To do the merge, do
-------------------------------------------------
-$ git-read-tree -m -u <origtree> <yourtree> <targettree>
+$ git read-tree -m -u <origtree> <yourtree> <targettree>
-------------------------------------------------
which will do all trivial merge operations for you directly in the
index file, and you can just write the result out with
-`git-write-tree`.
+`git write-tree`.
[[merging-multiple-trees-2]]
object, and you will have to resolve any such merge clashes using
other tools before you can write out the result.
-You can examine such index state with `git-ls-files --unmerged`
+You can examine such index state with `git ls-files --unmerged`
command. An example:
------------------------------------------------
-$ git-read-tree -m $orig HEAD $target
-$ git-ls-files --unmerged
+$ git read-tree -m $orig HEAD $target
+$ git ls-files --unmerged
100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello.c
100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello.c
100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello.c
------------------------------------------------
-Each line of the `git-ls-files --unmerged` output begins with
-the blob mode bits, blob SHA1, 'stage number', and the
+Each line of the `git ls-files --unmerged` output begins with
+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 `$target` the same way,
obviously the final outcome is what is in `HEAD`. What the
the blob objects from these three stages yourself, like this:
------------------------------------------------
-$ git-cat-file blob 263414f... >hello.c~1
-$ git-cat-file blob 06fa6a2... >hello.c~2
-$ git-cat-file blob cc44c73... >hello.c~3
+$ git cat-file blob 263414f... >hello.c~1
+$ git cat-file blob 06fa6a2... >hello.c~2
+$ git cat-file blob cc44c73... >hello.c~3
$ git merge-file hello.c~2 hello.c~1 hello.c~3
------------------------------------------------
-------------------------------------------------
$ mv -f hello.c~2 hello.c
-$ git-update-index hello.c
+$ git update-index hello.c
-------------------------------------------------
-When a path is in 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, uses three `git-cat-file`
-for this. There is `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
+$ git merge-index git-merge-one-file hello.c
-------------------------------------------------
and that is what higher level `git merge -s resolve` is implemented with.
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
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).
README in that revision uses the word "changeset" to describe what we
now call a <<def_commit_object,commit>>.
-Also, we do not call it "cache" any more, but "index", however, the
+Also, we do not call it "cache" any more, but rather "index"; however, the
file is still called `cache.h`. Remark: Not much reason to change it now,
especially since there is no good single name for it anyway, because it is
basically _the_ header file which is included by _all_ of Git's C sources.
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`.
+`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
If you are interested in more details of the revision walking process,
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
+`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
------------------------------------------------------------------
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]);
------------------------------------------------------------------
* 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
-----------------------------------------------
- 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
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