'\" t
.\" Title: gitglossary
.\" Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.75.2 <http://docbook.sf.net/>
.\" Date: 08/19/2012
.\" Manual: Git Manual
.\" Source: Git 1.7.12
.\" Language: English
.\"
.TH "GITGLOSSARY" "7" "08/19/2012" "Git 1\&.7\&.12" "Git Manual"
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.SH "NAME"
gitglossary \- A GIT Glossary
.SH "SYNOPSIS"
.sp
*
.SH "DESCRIPTION"
.PP
alternate object database
.RS 4
Via the alternates mechanism, a
repository
can inherit part of its
object database
from another object database, which is called "alternate"\&.
.RE
.PP
bare repository
.RS 4
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\&.
.RE
.PP
blob object
.RS 4
Untyped
object, e\&.g\&. the contents of a file\&.
.RE
.PP
branch
.RS 4
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\&.
.RE
.PP
cache
.RS 4
Obsolete for:
index\&.
.RE
.PP
chain
.RS 4
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)\&.
.RE
.PP
changeset
.RS 4
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\&.
.RE
.PP
checkout
.RS 4
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\&.
.RE
.PP
cherry\-picking
.RS 4
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\&.
.RE
.PP
clean
.RS 4
A
working tree
is clean, if it corresponds to the
revision
referenced by the current
head\&. Also see "dirty"\&.
.RE
.PP
commit
.RS 4
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\&.
.sp
As a verb: The action of storing a new snapshot of the project\(cqs 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\&.
.RE
.PP
commit object
.RS 4
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\&.
.RE
.PP
core git
.RS 4
Fundamental data structures and utilities of git\&. Exposes only limited source code management tools\&.
.RE
.PP
DAG
.RS 4
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)\&.
.RE
.PP
dangling object
.RS 4
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\&.
.RE
.PP
detached HEAD
.RS 4
Normally the
HEAD
stores the name of a
branch\&. However, git also allows you to
check out
an arbitrary
commit
that isn\(cqt necessarily the tip of any particular branch\&. In this case HEAD is said to be "detached"\&.
.RE
.PP
dircache
.RS 4
You are
\fBwaaaaay\fR
behind\&. See
index\&.
.RE
.PP
directory
.RS 4
The list you get with "ls" :\-)
.RE
.PP
dirty
.RS 4
A
working tree
is said to be "dirty" if it contains modifications which have not been
committed
to the current
branch\&.
.RE
.PP
ent
.RS 4
Favorite synonym to "tree\-ish" by some total geeks\&. See
\m[blue]\fBhttp://en\&.wikipedia\&.org/wiki/Ent_(Middle\-earth\fR\m[]) for an in\-depth explanation\&. Avoid this term, not to confuse people\&.
.RE
.PP
evil merge
.RS 4
An evil merge is a
merge
that introduces changes that do not appear in any
parent\&.
.RE
.PP
fast\-forward
.RS 4
A fast\-forward is a special type of
merge
where you have a
revision
and you are "merging" another
branch\(aqs 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\&.
.RE
.PP
fetch
.RS 4
Fetching a
branch
means to get the branch\(cqs
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
\fBgit-fetch\fR(1)\&.
.RE
.PP
file system
.RS 4
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\&.
.RE
.PP
git archive
.RS 4
Synonym for
repository
(for arch people)\&.
.RE
.PP
grafts
.RS 4
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\&.
.RE
.PP
hash
.RS 4
In git\(cqs context, synonym to
object name\&.
.RE
.PP
head
.RS 4
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
\fBgit-pack-refs\fR(1)\&.)
.RE
.PP
HEAD
.RS 4
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\&.
.RE
.PP
head ref
.RS 4
A synonym for
head\&.
.RE
.PP
hook
.RS 4
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\&.
.RE
.PP
index
.RS 4
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\&.
.RE
.PP
index entry
.RS 4
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)\&.
.RE
.PP
master
.RS 4
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\&.
.RE
.PP
merge
.RS 4
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\&.
.sp
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"\&.
.RE
.PP
object
.RS 4
The unit of storage in git\&. It is uniquely identified by the
SHA1
of its contents\&. Consequently, an object can not be changed\&.
.RE
.PP
object database
.RS 4
Stores a set of "objects", and an individual
object
is identified by its
object name\&. The objects usually live in
$GIT_DIR/objects/\&.
.RE
.PP
object identifier
.RS 4
Synonym for
object name\&.
.RE
.PP
object name
.RS 4
The unique identifier of an
object\&. The
hash
of the object\(cqs contents using the Secure Hash Algorithm 1 and usually represented by the 40 character hexadecimal encoding of the
hash
of the object\&.
.RE
.PP
object type
.RS 4
One of the identifiers "commit", "tree", "tag" or "blob" describing the type of an
object\&.
.RE
.PP
octopus
.RS 4
To
merge
more than two
branches\&. Also denotes an intelligent predator\&.
.RE
.PP
origin
.RS 4
The default upstream
repository\&. Most projects have at least one upstream project which they track\&. By default
\fIorigin\fR
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\&.
.RE
.PP
pack
.RS 4
A set of objects which have been compressed into one file (to save space or to transmit them efficiently)\&.
.RE
.PP
pack index
.RS 4
The list of identifiers, and other information, of the objects in a
pack, to assist in efficiently accessing the contents of a pack\&.
.RE
.PP
pathspec
.RS 4
Pattern used to specify paths\&.
.sp
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:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
any path matches itself
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
the pathspec up to the last slash represents a directory prefix\&. The scope of that pathspec is limited to that subtree\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
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,
\fI*\fR
and
\fI?\fR
\fIcan\fR
match directory separators\&.
.sp
For example, Documentation/*\&.jpg will match all \&.jpg files in the Documentation subtree, including Documentation/chapter_1/figure_1\&.jpg\&.
.RE
.sp
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\&.
.sp
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\&.
.sp
The "magic signature" consists of an ASCII symbol that is not alphanumeric\&.
.PP
top /
.RS 4
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\&.
.RE
.sp
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\&.
.sp
A pathspec with only a colon means "there is no pathspec"\&. This form should not be combined with other pathspec\&.
.RE
.PP
parent
.RS 4
A
commit object
contains a (possibly empty) list of the logical predecessor(s) in the line of development, i\&.e\&. its parents\&.
.RE
.PP
pickaxe
.RS 4
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
\fBgit-diff\fR(1)\&.
.RE
.PP
plumbing
.RS 4
Cute name for
core git\&.
.RE
.PP
porcelain
.RS 4
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\&.
.RE
.PP
pull
.RS 4
Pulling a
branch
means to
fetch
it and
merge
it\&. See also
\fBgit-pull\fR(1)\&.
.RE
.PP
push
.RS 4
Pushing a
branch
means to get the branch\(cqs
head ref
from a remote
repository, find out if it is a direct ancestor to the branch\(cqs 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\&.
.RE
.PP
reachable
.RS 4
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\&.
.RE
.PP
rebase
.RS 4
To reapply a series of changes from a
branch
to a different base, and reset the
head
of that branch to the result\&.
.RE
.PP
ref
.RS 4
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\&.
.RE
.PP
reflog
.RS 4
A reflog shows the local "history" of a ref\&. In other words, it can tell you what the 3rd last revision in
\fIthis\fR
repository was, and what was the current state in
\fIthis\fR
repository, yesterday 9:14pm\&. See
\fBgit-reflog\fR(1)
for details\&.
.RE
.PP
refspec
.RS 4
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
\fBgit-push\fR(1)\&.
.RE
.PP
remote\-tracking branch
.RS 4
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\&.
.RE
.PP
repository
.RS 4
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\&.
.RE
.PP
resolve
.RS 4
The action of fixing up manually what a failed automatic
merge
left behind\&.
.RE
.PP
revision
.RS 4
A particular state of files and directories which was stored in the
object database\&. It is referenced by a
commit object\&.
.RE
.PP
rewind
.RS 4
To throw away part of the development, i\&.e\&. to assign the
head
to an earlier
revision\&.
.RE
.PP
SCM
.RS 4
Source code management (tool)\&.
.RE
.PP
SHA1
.RS 4
Synonym for
object name\&.
.RE
.PP
shallow repository
.RS 4
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
\fBgit-clone\fR(1), and its history can be later deepened with
\fBgit-fetch\fR(1)\&.
.RE
.PP
symref
.RS 4
Symbolic reference: instead of containing the
SHA1
id itself, it is of the format
\fIref: refs/some/thing\fR
and when referenced, it recursively dereferences to this reference\&.
\fIHEAD\fR
is a prime example of a symref\&. Symbolic references are manipulated with the
\fBgit-symbolic-ref\fR(1)
command\&.
.RE
.PP
tag
.RS 4
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\(cqs context)\&. A tag is most typically used to mark a particular point in the commit ancestry
chain\&.
.RE
.PP
tag object
.RS 4
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"\&.
.RE
.PP
topic branch
.RS 4
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\&.
.RE
.PP
tree
.RS 4
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)\&.
.RE
.PP
tree object
.RS 4
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\&.
.RE
.PP
tree\-ish
.RS 4
A
ref
pointing to either a
commit object, a
tree object, or a
tag object
pointing to a tag or commit or tree object\&.
.RE
.PP
unmerged index
.RS 4
An
index
which contains unmerged
index entries\&.
.RE
.PP
unreachable object
.RS 4
An
object
which is not
reachable
from a
branch,
tag, or any other reference\&.
.RE
.PP
upstream branch
.RS 4
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
\fIA\fR
is
\fIorigin/B\fR
sometimes we say "\fIA\fR
is tracking
\fIorigin/B\fR"\&.
.RE
.PP
working tree
.RS 4
The tree of actual checked out files\&. The working tree normally contains the contents of the
HEAD
commit\(cqs tree, plus any local changes that you have made but not yet committed\&.
.RE
.SH "SEE ALSO"
.sp
\fBgittutorial\fR(7), \fBgittutorial-2\fR(7), \fBgitcvs-migration\fR(7), \m[blue]\fBEveryday git\fR\m[]\&\s-2\u[1]\d\s+2, \m[blue]\fBThe Git User\(cqs Manual\fR\m[]\&\s-2\u[2]\d\s+2
.SH "GIT"
.sp
Part of the \fBgit\fR(1) suite\&.
.SH "NOTES"
.IP " 1." 4
Everyday git
.RS 4
\%git-htmldocs/everyday.html
.RE
.IP " 2." 4
The Git User\(cqs Manual
.RS 4
\%git-htmldocs/user-manual.html
.RE