GitGlossary

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Wikified version of GIT Glossary, with some links to pages on this wiki added.

This list is sorted alphabetically:

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.

bottom 

? is the top the present, or is bottom the present?

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.

See also: BranchesInGit.

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 the working tree to a revision which was stored in the object database.

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 different codebase. In GIT, this is performed by "`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.

See also: git-cherry-pick(1)

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 current HEAD (current branch 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.

conflict 
core git 

Fundamental data structures and utilities of git. Exposes only limited source code management (SCM) 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.

downstream 

?

ent 

Favorite synonym to "tree-ish" by some total geeks. See Ent (Middle-earth) at Wikipedia for an in-depth explanation. Avoid this term, not to confuse people. It should be not used anymore.

evil merge 

An evil merge is a merge that introduces changes that do not appear in any parent.

forward-port 

?

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.

See also: GraftPoint

hash 

In git's context, synonym to object name.

head 

A named reference to 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 (symbolic) 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 making them executable.

See also: Hooks used by git.

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.

See also: IndexFile

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).

loose object 

An object stored by itself in a file (as opposed to being packed together with other objects to save space).

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 conventional and 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. See also git-merge(1)

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 as 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 (possibly followed by a white space).

object type 

One of the identifiers "commit","tree","tag" and "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`".

Historical: Before separate remotes layout become default, 'origin' was default upstream tracking branch (usually for master branch; the rest of remote branches were mapped 1:1 directly into local branches). New upstream updates (from 'master') were fetched into this branch; you should never commit to it yourself.

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. Ancestry information can be changed (faked) using grafts.

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 an ancestor to the branch's local head ref is a direct, 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.

See also git-rebase(1)

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/`.

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 master head 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".

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).

stash [information] 

?

stat [information] 

?

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 [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".

tip 

Informal term for the most recent commit on a branch. The equivalent formal term is lower cased head.

top 

?

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.

track 

?

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 refspec.

trailer 

Different projects or tools have conventions to include machine parsable information in a header like format at the end of commit messages, e.g.:

Closes: #42
Thanks: my mother, my wife
Git-Dch: Ignore
Commit-Id: 50M3R34LLYR4ND0MB1TSANDNUMB3R5

(see thread: "RFE: support change-id generation natively" for Commit-Id) ("Git-Dch: Ignore" ecludes the commit from the changelog)

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 

?

working tree 

The tree of actual checked out files. The working tree is normally equal to the HEAD plus any local changes that you have made but not yet committed.

The set of files and directories currently being worked on, i.e. you can work in your working tree without using git at all.


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