| 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
"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 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 $GIT_DIR/refs/heads/, 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 may reference 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 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.
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. These may be stored in $GIT_DIR/refs/.
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).
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 pointing to a tag or commit object. In contrast to
a head, a tag is not changed by a commit. Tags (not tag objects) are stored in
$GIT_DIR/refs/tags/. 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.
tracking branch
A regular git branch that is used to follow changes from
another repository. A tracking branch should not contain direct modifications
or have local commits made to it. A tracking branch can usually be identified
as the right-hand-side ref in a Pull: refspec.
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 ALSO¶
gittutorial(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
- 2.
- The Git User’s Manual
| 02/03/2020 | Git 1.7.1 |