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
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 available.

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

branch
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.

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 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.

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.

dereference
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 recursively.

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.

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 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.

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. For proper use see
git-worktree(1) or git-submodule(1). For syntax see
gitrepository-layout(5).

grafts
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.

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 cannot 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 (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.

octopus
To merge more than two branches.

orphan
The act of getting on a branch that does not exist yet (i.e., an
unborn branch). After such an operation, the commit first created
becomes a commit without a parent, starting a new history.

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

overlay
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.

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 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:

+o any path matches itself

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

+o 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 "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.

top
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.

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

icase
Case insensitive match.

glob
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 "tools/perf/Documentation/perf.html".

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

+o 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".

+o 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.

+o 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.

+o Other consecutive asterisks are considered invalid.

Glob magic is incompatible with literal magic.

attr
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 gitattributes(5).

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

+o "ATTR" requires that the attribute ATTR be set.

+o "-ATTR" requires that the attribute ATTR be unset.

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

+o "!ATTR" requires that the attribute ATTR be unspecified.

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

exclude
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 pathspec.

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

peel
The action of recursively dereferencing a tag object.

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.

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.

pseudoref
A ref that has different semantics than normal refs. These refs
can be read via normal Git commands, but cannot be written to by
commands like git-update-ref(1).

The following pseudorefs are known to Git:

+o FETCH_HEAD is written by git-fetch(1) or git-pull(1). It may
refer to multiple object IDs. Each object ID is annotated
with metadata indicating where it was fetched from and its
fetch status.

+o MERGE_HEAD is written by git-merge(1) when resolving merge
conflicts. It contains all commit IDs which are being merged.

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 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 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.

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).

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 name 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 repository.

The ref namespace is hierarchical. Ref names must either start
with refs/ or be located in the root of the hierarchy. For the
latter, their name must follow these rules:

+o The name consists of only upper-case characters or
underscores.

+o The name ends with "_HEAD" or is equal to "HEAD".

There are some irregular refs in the root of the hierarchy
that do not match these rules. The following list is
exhaustive and shall not be extended in the future:

+o AUTO_MERGE

+o BISECT_EXPECTED_REV

+o NOTES_MERGE_PARTIAL

+o NOTES_MERGE_REF

+o MERGE_AUTOSTASH

Different subhierarchies are used for different purposes. For
example, the refs/heads/ hierarchy is used to represent local
branches whereas the refs/tags/ hierarchy is used to
represent local tags..

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. See git-fetch(1) or git-push(1)
for details.

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.

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 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.

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

superproject
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.

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.

trailer
Key-value metadata. Trailers are optionally found at the end of a
commit message. Might be called "footers" or "tags" in other
communities. See git-interpret-trailers(1).

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 (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.

unborn
The HEAD can point at a branch that does not yet exist and that
does not have any commit on it yet, and such a branch is called
an unborn branch. The most typical way users encounter an unborn
branch is by creating a repository anew without cloning from
elsewhere. The HEAD would point at the main (or master, depending
on your configuration) branch that is yet to be born. Also some
operations can get you on an unborn branch with their orphan
option.

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.

worktree
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

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

GIT

Part of the git(1) suite

NOTES

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

Git 2.48.1 2025-01-13 GITGLOSSARY(7)