gitglossary(7) — Linux manual page


GITGLOSSARY(7)                 Git Manual                 GITGLOSSARY(7)

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       gitglossary - A Git Glossary

SYNOPSIS         top


DESCRIPTION         top

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

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

           A "branch" is a 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

           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 graph concept, representations and usage
           A synonym for the DAG structure formed by the commits in the
           object database, referenced by branch tips, using their chain
           of linked commits. This structure is the definitive commit
           graph. The graph can be represented in other ways, e.g. the
           "commit-graph" file.

       commit-graph file
           The "commit-graph" (normally hyphenated) file is a
           supplemental representation of the commit graph which
           accelerates commit graph walks. The "commit-graph" file is
           stored either in the .git/objects/info directory or in the
           info directory of an alternate object database.

       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.

       commit-ish (also committish)
           A commit object or an object that can be recursively
           dereferenced to a commit object. The following are all
           commit-ishes: a commit object, a tag object that points to a
           commit object, a tag object that points to a tag object that
           points to a commit object, etc.

       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.

           Referring to a symbolic ref: the action of accessing the
           reference pointed at by a symbolic ref. Recursive
           dereferencing involves repeating the aforementioned process
           on the resulting ref until a non-symbolic reference is found.

           Referring to a tag object: the action of accessing the object
           a tag points at. Tags are recursively dereferenced by
           repeating the operation on the result object until the result
           has either a specified object type (where applicable) or any
           non-"tag" object type. A synonym for "recursive dereference"
           in the context of tags is "peel".

           Referring to a commit object: the action of accessing the
           commit’s tree object. Commits cannot be dereferenced

           Unless otherwise specified, "dereferencing" as it used in the
           context of Git commands or protocols is implicitly recursive.

       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.

           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

       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 a case,
           you do not make a new merge commit but instead just update
           your branch to point at the same revision as the branch you
           are merging. This will happen frequently on a remote-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

       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).

           A plain file .git at the root of a working tree that points
           at the directory that is the real repository. For proper use
           see git-worktree(1) or git-submodule(1). For syntax see

           Grafts enable 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.

           Note that the grafts mechanism is outdated and can lead to
           problems transferring objects between repositories; see
           git-replace(1) for a more flexible and robust system to do
           the same thing.

           In Git’s context, synonym for object name.

           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).)

           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.

           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

           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).

           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

           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".

           The unit of storage in Git. It is uniquely identified by the
           SHA-1 of its contents. Consequently, an object cannot be

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

       object identifier (oid)
           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.

           To merge more than two branches.

           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.

           Only update and add files to the working directory, but don’t
           delete them, similar to how cp -R would update the contents
           in the destination directory. This is the default mode in a
           checkout when checking out files from the index or a
           tree-ish. In contrast, no-overlay mode also deletes tracked
           files not present in the source, similar to rsync --delete.

           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.

           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 working tree. 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

           •   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

           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 "magic signature"
           consists of ASCII symbols that are neither alphanumeric,
           glob, regex special characters nor colon. The optional colon
           that terminates the "magic signature" can be omitted if the
           pattern begins with a character that does not belong to
           "magic signature" symbol set and is not a colon.

           In the long form, the leading colon : is followed by an 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.

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

               The magic word top (magic signature: /) makes the pattern
               match from the root of the working tree, even when you
               are running the command from inside a subdirectory.

               Wildcards in the pattern such as * or ?  are treated as
               literal characters.

               Case insensitive match.

               Git treats the pattern as a shell glob suitable for
               consumption by fnmatch(3) with the FNM_PATHNAME flag:
               wildcards in the pattern will not match a / in the
               pathname. For example, "Documentation/*.html" matches
               "Documentation/git.html" but not
               "Documentation/ppc/ppc.html" or

               Two consecutive asterisks ("**") in patterns matched
               against full pathname may have special meaning:

               •   A leading "**" followed by a slash means match in all
                   directories. For example, "**/foo" matches file or
                   directory "foo" anywhere, the same as pattern "foo".
                   "**/foo/bar" matches file or directory "bar" anywhere
                   that is directly under directory "foo".

               •   A trailing "/**" matches everything inside. For
                   example, "abc/**" matches all files inside directory
                   "abc", relative to the location of the .gitignore
                   file, with infinite depth.

               •   A slash followed by two consecutive asterisks then a
                   slash matches zero or more directories. For example,
                   "a/**/b" matches "a/b", "a/x/b", "a/x/y/b" and so on.

               •   Other consecutive asterisks are considered invalid.

                   Glob magic is incompatible with literal magic.

               After attr: comes a space separated list of "attribute
               requirements", all of which must be met in order for the
               path to be considered a match; this is in addition to the
               usual non-magic pathspec pattern matching. See

               Each of the attribute requirements for the path takes one
               of these forms:

               •   "ATTR" requires that the attribute ATTR be set.

               •   "-ATTR" requires that the attribute ATTR be unset.

               •   "ATTR=VALUE" requires that the attribute ATTR be set
                   to the string VALUE.

               •   "!ATTR" requires that the attribute ATTR be

                   Note that when matching against a tree object,
                   attributes are still obtained from working tree, not
                   from the given tree object.

               After a path matches any non-exclude pathspec, it will be
               run through all exclude pathspecs (magic signature: !  or
               its synonym ^). If it matches, the path is ignored. When
               there is no non-exclude pathspec, the exclusion is
               applied to the result set as if invoked without any

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

           The action of recursively dereferencing a tag object.

           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).

           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.

       per-worktree ref
           Refs that are per-worktree, rather than global. This is
           presently only HEAD and any refs that start with
           refs/bisect/, but might later include other unusual refs.

           Pseudorefs are a class of files under $GIT_DIR which behave
           like refs for the purposes of rev-parse, but which are
           treated specially by git. Pseudorefs both have names that are
           all-caps, and always start with a line consisting of a SHA-1
           followed by whitespace. So, HEAD is not a pseudoref, because
           it is sometimes a symbolic ref. They might optionally contain
           some additional data.  MERGE_HEAD and CHERRY_PICK_HEAD are
           examples. Unlike per-worktree refs, these files cannot be
           symbolic refs, and never have reflogs. They also cannot be
           updated through the normal ref update machinery. Instead,
           they are updated by directly writing to the files. However,
           they can be read as if they were refs, so git rev-parse
           MERGE_HEAD will work.

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

           Pushing a branch means to get the branch’s head ref from a
           remote repository, find out if it is an 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

           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.

       reachability bitmaps
           Reachability bitmaps store information about the reachability
           of a selected set of commits in a packfile, or a multi-pack
           index (MIDX), to speed up object search. The bitmaps are
           stored in a ".bitmap" file. A repository may have at most one
           bitmap file in use. The bitmap file may belong to either one
           pack, or the repository’s multi-pack index (if it exists).

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

           A name that begins with refs/ (e.g.  refs/heads/master) that
           points to an object name or another ref (the latter is called
           a symbolic ref). For convenience, a ref can sometimes be
           abbreviated when used as an argument to a Git command; see
           gitrevisions(7) for details. Refs are stored in the

           The ref namespace is hierarchical. Different subhierarchies
           are used for different purposes (e.g. the refs/heads/
           hierarchy is used to represent local branches).

           There are a few special-purpose refs that do not begin with
           refs/. The most notable example is HEAD.

           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.

       remote repository
           A repository which is used to track the same project but
           resides somewhere else. To communicate with remotes, see
           fetch or push.

       remote-tracking branch
           A ref that is used to follow changes from another repository.
           It typically looks like refs/remotes/foo/bar (indicating that
           it tracks a branch named bar in a remote named foo), and
           matches the right-hand-side of a configured fetch refspec. A
           remote-tracking branch should not contain direct
           modifications or have local commits made to it.

           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 behind.

           Synonym for commit (the noun).

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

           Source code management (tool).

           "Secure Hash Algorithm 1"; a cryptographic hash function. In
           the context of Git used as a synonym for object name.

       shallow clone
           Mostly a synonym to shallow repository but the phrase makes
           it more explicit that it was created by running git clone
           --depth=...  command.

       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).

       stash entry
           An object used to temporarily store the contents of a dirty
           working directory and the index for future reuse.

           A repository that holds the history of a separate project
           inside another repository (the latter of which is called

           A repository that references repositories of other projects
           in its working tree as submodules. The superproject knows
           about the names of (but does not hold copies of) commit
           objects of the contained submodules.

           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.

           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.

           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 (also treeish)
           A tree object or an object that can be recursively
           dereferenced to a tree object. Dereferencing a commit object
           yields the tree object corresponding to the revision's top
           directory. The following are all tree-ishes: a commit-ish, a
           tree object, a tag object that points to a tree object, a tag
           object that points to a tag object that points to a tree
           object, etc.

       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

           A repository can have zero (i.e. bare repository) or one or
           more worktrees attached to it. One "worktree" consists of a
           "working tree" and repository metadata, most of which are
           shared among other worktrees of a single repository, and some
           of which are maintained separately per worktree (e.g. the
           index, HEAD and pseudorefs like MERGE_HEAD, per-worktree refs
           and per-worktree configuration file).

SEE ALSO         top

       gittutorial(7), gittutorial-2(7), gitcvs-migration(7),
       giteveryday(7), The Git User’s Manual[1]

GIT         top

       Part of the git(1) suite

NOTES         top

        1. The Git User’s Manual

COLOPHON         top

       This page is part of the git (Git distributed version control
       system) project.  Information about the project can be found at
       ⟨⟩.  If you have a bug report for this manual
       page, see ⟨⟩.  This page was obtained
       from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.  (At that time,
       the date of the most recent commit that was found in the
       repository was 2023-12-20.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

Git         2023-12-20                 GITGLOSSARY(7)

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