NAME
gitglossary - A Git GlossarySYNOPSIS
*DESCRIPTION
alternate object databaseVia 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.
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.
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.
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.
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:
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
parent
•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.
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:
attr
•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 gitattributes(5).
Each of the attribute requirements for the path takes one of these forms:
exclude
•"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 unspecified.
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 pathspec.
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.
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
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.
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 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 repository.
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.
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 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.
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.
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) suiteNOTES
- 1.
- The Git User’s Manual
file:///usr/share/doc/git/html/user-manual.html
02/28/2023 | Git 2.39.2 |