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       gitglossary - A GIT Glossary




       alternate object database
           Via the alternates mechanism, a repository can inherit part of its
           object database from another object database, which is called

       bare repository
           A bare repository is normally an appropriately named directory with
           a .git suffix that does not have a locally checked-out copy of any
           of the files under revision control. That is, all of the git
           administrative and control files that would normally be present in
           the hidden .git sub-directory are directly present in the
           repository.git directory instead, and no other files are present
           and checked out. Usually publishers of public repositories make
           bare repositories available.

       blob object
           Untyped object, e.g. the contents of a file.

           A "branch" is an active line of development. The most recent commit
           on a branch is referred to as the tip of that branch. The tip of
           the branch is referenced by a branch head, which moves forward as
           additional development is done on the branch. A single git
           repository can track an arbitrary number of branches, but your
           working tree is associated with just one of them (the "current" or
           "checked out" branch), and HEAD points to that branch.

           Obsolete for: index.

           A list of objects, where each object in the list contains a
           reference to its successor (for example, the successor of a commit
           could be one of its parents).

           BitKeeper/cvsps speak for "commit". Since git does not store
           changes, but states, it really does not make sense to use the term
           "changesets" with git.

           The action of updating all or part of the working tree with a tree
           object or blob from the object database, and updating the index and
           HEAD if the whole working tree has been pointed at a new branch.

           In SCM jargon, "cherry pick" means to choose a subset of changes
           out of a series of changes (typically commits) and record them as a
           new series of changes on top of a different codebase. In GIT, this
           is performed by the "git cherry-pick" command to extract the change
           introduced by an existing commit and to record it based on the tip
           of the current branch as a new commit.

           A working tree is clean, if it corresponds to the revision
           referenced by the current head. Also see "dirty".

           As a noun: A single point in the git history; the entire history of
           a project is represented as a set of interrelated commits. The word
           "commit" is often used by git in the same places other revision
           control systems use the words "revision" or "version". Also used as
           a short hand for commit object.

           As a verb: The action of storing a new snapshot of the project's
           state in the git history, by creating a new commit representing the
           current state of the index and advancing HEAD to point at the new

       commit object
           An object which contains the information about a particular
           revision, such as parents, committer, author, date and the tree
           object which corresponds to the top directory of the stored

       core git
           Fundamental data structures and utilities of git. Exposes only
           limited source code management tools.

           Directed acyclic graph. The commit objects form a directed acyclic
           graph, because they have parents (directed), and the graph of
           commit objects is acyclic (there is no chain which begins and ends
           with the same object).

       dangling object
           An unreachable object which is not reachable even from other
           unreachable objects; a dangling object has no references to it from
           any reference or object in the repository.

       detached HEAD
           Normally the HEAD stores the name of a branch. However, git also
           allows you to check out an arbitrary commit that isn't necessarily
           the tip of any particular branch. In this case HEAD is said to be

           You are waaaaay behind. See index.

           The list you get with "ls" :-)

           A working tree is said to be "dirty" if it contains modifications
           which have not been committed to the current branch.

           Favorite synonym to "tree-ish" by some total geeks. See
  for an in-depth
           explanation. Avoid this term, not to confuse people.

       evil merge
           An evil merge is a merge that introduces changes that do not appear
           in any parent.

           A fast-forward is a special type of merge where you have a revision
           and you are "merging" another branch's changes that happen to be a
           descendant of what you have. In such these cases, you do not make a
           new merge commit but instead just update to his revision. This will
           happen frequently on a tracking branch of a remote repository.

           Fetching a branch means to get the branch's head ref from a remote
           repository, to find out which objects are missing from the local
           object database, and to get them, too. See also git-fetch(1).

       file system
           Linus Torvalds originally designed git to be a user space file
           system, i.e. the infrastructure to hold files and directories. That
           ensured the efficiency and speed of git.

       git archive
           Synonym for repository (for arch people).

           Grafts enables two otherwise different lines of development to be
           joined together by recording fake ancestry information for commits.
           This way you can make git pretend the set of parents a commit has
           is different from what was recorded when the commit was created.
           Configured via the .git/info/grafts file.

           In git's context, synonym to object name.

           A named reference to the commit at the tip of a branch. Heads are
           stored in $GIT_DIR/refs/heads/, except when using packed refs. (See

           The current branch. In more detail: Your working tree is normally
           derived from the state of the tree referred to by HEAD. HEAD is a
           reference to one of the heads in your repository, except when using
           a detached HEAD, in which case it may reference an arbitrary

       head ref
           A synonym for head.

           During the normal execution of several git commands, call-outs are
           made to optional scripts that allow a developer to add
           functionality or checking. Typically, the hooks allow for a command
           to be pre-verified and potentially aborted, and allow for a
           post-notification after the operation is done. The hook scripts are
           found in the $GIT_DIR/hooks/ directory, and are enabled by simply
           removing the .sample suffix from the filename. In earlier versions
           of git you had to make them executable.

           A collection of files with stat information, whose contents are
           stored as objects. The index is a stored version of your working
           tree. Truth be told, it can also contain a second, and even a third
           version of a working tree, which are used when merging.

       index entry
           The information regarding a particular file, stored in the index.
           An index entry can be unmerged, if a merge was started, but not yet
           finished (i.e. if the index contains multiple versions of that

           The default development branch. Whenever you create a git
           repository, a branch named "master" is created, and becomes the
           active branch. In most cases, this contains the local development,
           though that is purely by convention and is not required.

           As a verb: To bring the contents of another branch (possibly from
           an external repository) into the current branch. In the case where
           the merged-in branch is from a different repository, this is done
           by first fetching the remote branch and then merging the result
           into the current branch. This combination of fetch and merge
           operations is called a pull. Merging is performed by an automatic
           process that identifies changes made since the branches diverged,
           and then applies all those changes together. In cases where changes
           conflict, manual intervention may be required to complete the

           As a noun: unless it is a fast-forward, a successful merge results
           in the creation of a new commit representing the result of the
           merge, and having as parents the tips of the merged branches. This
           commit is referred to as a "merge commit", or sometimes just a

           The unit of storage in git. It is uniquely identified by the SHA1
           of its contents. Consequently, an object can not be changed.

       object database
           Stores a set of "objects", and an individual object is identified
           by its object name. The objects usually live in $GIT_DIR/objects/.

       object identifier
           Synonym for object name.

       object name
           The unique identifier of an object. The hash of the object's
           contents using the Secure Hash Algorithm 1 and usually represented
           by the 40 character hexadecimal encoding of the hash of the object.

       object type
           One of the identifiers "commit", "tree", "tag" or "blob" describing
           the type of an object.

           To merge more than two branches. Also denotes an intelligent

           The default upstream repository. Most projects have at least one
           upstream project which they track. By default origin is used for
           that purpose. New upstream updates will be fetched into remote
           tracking branches named origin/name-of-upstream-branch, which you
           can see using git branch -r.

           A set of objects which have been compressed into one file (to save
           space or to transmit them efficiently).

       pack index
           The list of identifiers, and other information, of the objects in a
           pack, to assist in efficiently accessing the contents of a pack.

           A commit object contains a (possibly empty) list of the logical
           predecessor(s) in the line of development, i.e. its parents.

           The term pickaxe refers to an option to the diffcore routines that
           help select changes that add or delete a given text string. With
           the --pickaxe-all option, it can be used to view the full changeset
           that introduced or removed, say, a particular line of text. See

           Cute name for core git.

           Cute name for programs and program suites depending on core git,
           presenting a high level access to core git. Porcelains expose more
           of a SCM interface than the plumbing.

           Pulling a branch means to fetch it and merge it. See also git-

           Pushing a branch means to get the branch's head ref from a remote
           repository, find out if it is a direct ancestor to the branch's
           local head ref, and in that case, putting all objects, which are
           reachable from the local head ref, and which are missing from the
           remote repository, into the remote object database, and updating
           the remote head ref. If the remote head is not an ancestor to the
           local head, the push fails.

           All of the ancestors of a given commit are said to be "reachable"
           from that commit. More generally, one object is reachable from
           another if we can reach the one from the other by a chain that
           follows tags to whatever they tag, commits to their parents or
           trees, and trees to the trees or blobs that they contain.

           To reapply a series of changes from a branch to a different base,
           and reset the head of that branch to the result.

           A 40-byte hex representation of a SHA1 or a name that denotes a
           particular object. These may be stored in $GIT_DIR/refs/.

           A reflog shows the local "history" of a ref. In other words, it can
           tell you what the 3rd last revision in this repository was, and
           what was the current state in this repository, yesterday 9:14pm.
           See git-reflog(1) for details.

           A "refspec" is used by fetch and push to describe the mapping
           between remote ref and local ref. They are combined with a colon in
           the format <src>:<dst>, preceded by an optional plus sign, +. For
           example: git fetch $URL refs/heads/master:refs/heads/origin means
           "grab the master branch head from the $URL and store it as my
           origin branch head". And git push $URL
           refs/heads/master:refs/heads/to-upstream means "publish my master
           branch head as to-upstream branch at $URL". See also git-push(1).

           A collection of refs together with an object database containing
           all objects which are reachable from the refs, possibly accompanied
           by meta data from one or more porcelains. A repository can share an
           object database with other repositories via alternates mechanism.

           The action of fixing up manually what a failed automatic merge left

           A particular state of files and directories which was stored in the
           object database. It is referenced by a commit object.

           To throw away part of the development, i.e. to assign the head to
           an earlier revision.

           Source code management (tool).

           Synonym for object name.

       shallow repository
           A shallow repository has an incomplete history some of whose
           commits have parents cauterized away (in other words, git is told
           to pretend that these commits do not have the parents, even though
           they are recorded in the commit object). This is sometimes useful
           when you are interested only in the recent history of a project
           even though the real history recorded in the upstream is much
           larger. A shallow repository is created by giving the --depth
           option to git-clone(1), and its history can be later deepened with

           Symbolic reference: instead of containing the SHA1 id itself, it is
           of the format ref: refs/some/thing and when referenced, it
           recursively dereferences to this reference.  HEAD is a prime
           example of a symref. Symbolic references are manipulated with the
           git-symbolic-ref(1) command.

           A ref pointing to a tag or commit object. In contrast to a head, a
           tag is not changed by a commit. Tags (not tag objects) are stored
           in $GIT_DIR/refs/tags/. A git tag has nothing to do with a Lisp tag
           (which would be called an object type in git's context). A tag is
           most typically used to mark a particular point in the commit
           ancestry chain.

       tag object
           An object containing a ref pointing to another object, which can
           contain a message just like a commit object. It can also contain a
           (PGP) signature, in which case it is called a "signed tag object".

       topic branch
           A regular git branch that is used by a developer to identify a
           conceptual line of development. Since branches are very easy and
           inexpensive, it is often desirable to have several small branches
           that each contain very well defined concepts or small incremental
           yet related changes.

       tracking branch
           A regular git branch that is used to follow changes from another
           repository. A tracking branch should not contain direct
           modifications or have local commits made to it. A tracking branch
           can usually be identified as the right-hand-side ref in a Pull:

           Either a working tree, or a tree object together with the dependent
           blob and tree objects (i.e. a stored representation of a working

       tree object
           An object containing a list of file names and modes along with refs
           to the associated blob and/or tree objects. A tree is equivalent to
           a directory.

           A ref pointing to either a commit object, a tree object, or a tag
           object pointing to a tag or commit or tree object.

       unmerged index
           An index which contains unmerged index entries.

       unreachable object
           An object which is not reachable from a branch, tag, or any other

       upstream branch
           The default branch that is merged into the branch in question (or
           the branch in question is rebased onto). It is configured via
           branch.<name>.remote and branch.<name>.merge. If the upstream
           branch of A is origin/B sometimes we say "A is tracking origin/B".

       working tree
           The tree of actual checked out files. The working tree normally
           contains the contents of the HEAD commit's tree, plus any local
           changes that you have made but not yet committed.


       gittutorial(7), gittutorial-2(7), gitcvs-migration(7), Everyday git[1],
       The Git User's Manual[2]


       Part of the git(1) suite.


        1. Everyday git

        2. The Git User's Manual