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GITGLOSSARY(7)                                   Git Manual                                   GITGLOSSARY(7)



NAME
       gitglossary - A Git Glossary

SYNOPSIS
       *

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

       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.

       branch
           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.

       cache
           Obsolete for: index.

       chain
           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).

       changeset
           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.

       checkout
           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.

       cherry-picking
           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.

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

       commit
           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.

       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 revision.

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

       DAG
           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, and commands that operate on the history HEAD
           represents operate on the history leading to the tip of the branch the HEAD points at. However,
           Git also allows you to check out an arbitrary commit that isn't necessarily the tip of any
           particular branch. The HEAD in such a state is called "detached".

           Note that commands that operate on the history of the current branch (e.g.  git commit to build a
           new history on top of it) still work while the HEAD is detached. They update the HEAD to point at
           the tip of the updated history without affecting any branch. Commands that update or inquire
           information about the current branch (e.g.  git branch --set-upstream-to that sets what remote
           tracking branch the current branch integrates with) obviously do not work, as there is no (real)
           current branch to ask about in this state.

       directory
           The list you get with "ls" :-)

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

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

       fast-forward
           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
           remote-tracking branch of a remote repository.

       fetch
           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).

       gitfile
           A plain file .git at the root of a working tree that points at the directory that is the real
           repository.

       grafts
           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.

       hash
           In Git's context, synonym for object name.

       head
           A named reference to the commit at the tip of a branch. Heads are stored in a file in
           $GIT_DIR/refs/heads/ directory, except when using packed refs. (See git-pack-refs(1).)

       HEAD
           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 directly references an arbitrary commit.

       head ref
           A synonym for head.

       hook
           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.

       index
           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 file).

       master
           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.

       merge
           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 merge.

           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 "merge".

       object
           The unit of storage in Git. It is uniquely identified by the SHA-1 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 object name is usually represented by a 40 character
           hexadecimal string. Also colloquially called SHA-1.

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

       octopus
           To merge more than two branches.

       origin
           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 remote-tracking branches named origin/name-of-upstream-branch, which you can see using git
           branch -r.

       pack
           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.

       pathspec
           Pattern used to limit paths in Git commands.

           Pathspecs are used on the command line of "git ls-files", "git ls-tree", "git add", "git grep",
           "git diff", "git checkout", and many other commands to limit the scope of operations to some
           subset of the tree or worktree. See the documentation of each command for whether paths are
           relative to the current directory or toplevel. The pathspec syntax is as follows:

           •   any path matches itself

           •   the pathspec up to the last slash represents a directory prefix. The scope of that pathspec
               is limited to that subtree.

           •   the rest of the pathspec is a pattern for the remainder of the pathname. Paths relative to
               the directory prefix will be matched against that pattern using fnmatch(3); in particular, *
               and ?  can match directory separators.

           For example, Documentation/*.jpg will match all .jpg files in the Documentation subtree,
           including Documentation/chapter_1/figure_1.jpg.

           A pathspec that begins with a colon : has special meaning. In the short form, the leading colon :
           is followed by zero or more "magic signature" letters (which optionally is terminated by another
           colon :), and the remainder is the pattern to match against the path. The optional colon that
           terminates the "magic signature" can be omitted if the pattern begins with a character that
           cannot be a "magic signature" and is not a colon.

           In the long form, the leading colon : is followed by a open parenthesis (, a comma-separated list
           of zero or more "magic words", and a close parentheses ), and the remainder is the pattern to
           match against the path.

           The "magic signature" consists of an ASCII symbol that is not alphanumeric. Currently only the
           slash / is recognized as a "magic signature": it makes the pattern match from the root of the
           working tree, even when you are running the command from inside a subdirectory.

           A pathspec with only a colon means "there is no pathspec". This form should not be combined with
           other pathspec.

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

       pickaxe
           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 git-diff(1).

       plumbing
           Cute name for core Git.

       porcelain
           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.

       pull
           Pulling a branch means to fetch it and merge it. See also git-pull(1).

       push
           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.

       reachable
           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.

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

       ref
           A 40-byte hex representation of a SHA-1 or a name that denotes a particular object. They may be
           stored in a file under $GIT_DIR/refs/ directory, or in the $GIT_DIR/packed-refs file.

       reflog
           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.

       refspec
           A "refspec" is used by fetch and push to describe the mapping between remote ref and local ref.

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

       repository
           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.

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

       revision
           Synonym for commit (the noun).

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

       SCM
           Source code management (tool).

       SHA-1
           "Secure Hash Algorithm 1"; a cryptographic hash function. In the context of Git used as a 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 git-fetch(1).

       symref
           Symbolic reference: instead of containing the SHA-1 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.

       tag
           A ref under refs/tags/ namespace that points to an object of an arbitrary type (typically a tag
           points to either a tag or a commit object). In contrast to a head, a tag is not updated by the
           commit command. 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.

       tree
           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).

       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.

       tree-ish
           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 reference.

       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.

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

GIT
       Part of the git(1) suite.

NOTES
        1. Everyday Git
           git-htmldocs/everyday.html

        2. The Git User's Manual
           git-htmldocs/user-manual.html



Git 1.8.3                                        05/24/2013                                   GITGLOSSARY(7)