GITGLOSSARY(7) Git Manual GITGLOSSARY(7)NAMEgitglossary - 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. However, git also
allows you to check out an arbitrary commit that isn’t necessarily
the tip of any particular branch. In this case HEAD is said to be
"detached".
dircache
You are waaaaay behind. See index.
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.
ent
Favorite synonym to "tree-ish" by some total geeks. See
http://en.wikipedia.org/wiki/Ent_(Middle-earth) for an in-depth
explanation. Avoid this term, not to confuse people.
evil merge
An evil merge is a merge that introduces changes that do not appear
in any parent.
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).
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 to 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 SHA1
of its contents. Consequently, an object can not be changed.
object database
Stores a set of "objects", and an individual object is identified
by its object name. The objects usually live in $GIT_DIR/objects/.
object identifier
Synonym for object name.
object name
The unique identifier of an object. The hash of the object’s
contents using the Secure Hash Algorithm 1 and usually represented
by the 40 character hexadecimal encoding of the hash of the object.
object type
One of the identifiers "commit", "tree", "tag" or "blob" describing
the type of an object.
octopus
To merge more than two branches. Also denotes an intelligent
predator.
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 specify paths.
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.
top /
The magic word top (mnemonic: /) makes the pattern match
from the root of the working tree, even when you are
running the command from inside a subdirectory.
Currently only the slash / is recognized as the "magic
signature", but it is envisioned that we will support more
types of magic in later versions of git.
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 SHA1 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. They are combined with a
colon in the format <src>:<dst>, preceded by an optional plus
sign, +. For example: git fetch $URL
refs/heads/master:refs/heads/origin means "grab the master
branch head from the $URL and store it as my origin branch
head". And git push $URL
refs/heads/master:refs/heads/to-upstream means "publish my
master branch head as to-upstream branch at $URL". See also
git-push(1).
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
A particular state of files and directories which was stored in
the object database. It is referenced by a commit object.
rewind
To throw away part of the development, i.e. to assign the head
to an earlier revision.
SCM
Source code management (tool).
SHA1
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 SHA1 id itself,
it is of the format ref: refs/some/thing and when referenced,
it recursively dereferences to this reference. HEAD is a prime
example of a symref. Symbolic references are manipulated with
the git-symbolic-ref(1) command.
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 ALSOgittutorial(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
file:///opt/csw/share/doc/git-doc/everyday.html
2. The Git User’s Manual
file:///opt/csw/share/doc/git-doc/user-manual.html
Git 1.8.1.4 02/22/2013 GITGLOSSARY(7)
