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 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 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.

       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 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).

       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 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 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.

       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 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 "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 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.

           A pathspec with only a colon means "there is no pathspec". This form should not be combined with
           other pathspec.

           top
               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:

               •   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.

           attr
               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:

               •   "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.

           exclude
               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.

       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.

       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 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 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.

SEE ALSO

       gittutorial(7), gittutorial-2(7), gitcvs-migration(7), giteveryday(7), The Git User’s Manual[1]

GIT

       Part of the git(1) suite

NOTES

        1. The Git User’s Manual
           file:///usr/share/doc/git/html/user-manual.html