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       gitglossary - A Git Glossary




       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.

           A "branch" is a 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

           Obsolete for: index.

           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).

           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.

           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.

           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.

           A working tree is clean, if it corresponds to the revision referenced by the current
           head. Also see "dirty".

           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.

           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

       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

           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.

           The list you get with "ls" :-)

           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.

           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 your branch to
           point at the same revision as the branch you are merging. This will happen frequently
           on a remote-tracking branch of a remote repository.

           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 archive
           Synonym for repository (for arch people).

           A plain file .git at the root of a working tree that points at the directory that is
           the real repository.

           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.

           In Git’s context, synonym for object name.

           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).)

           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.

           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.

           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).

           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.

           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".

           The unit of storage in Git. It is uniquely identified by the SHA-1 of its contents.
           Consequently, an object cannot 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

           To merge more than two branches.

           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.

           Only update and add files to the working directory, but don’t delete them, similar to
           how cp -R would update the contents in the destination directory. This is the default
           mode in a checkout when checking out files from the index or a tree-ish. In contrast,
           no-overlay mode also deletes tracked files not present in the source, similar to rsync

           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.

           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 working tree. 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 an 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.

               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

               Wildcards in the pattern such as * or ?  are treated as literal characters.

               Case insensitive match.

               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.

               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.

                   Note that when matching against a tree object, attributes are still obtained
                   from working tree, not from the given tree object.

               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.

           A commit object contains a (possibly empty) list of the logical predecessor(s) in the
           line of development, i.e. its parents.

           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).

           Cute name for core Git.

           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.

           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.

           Pulling a branch means to fetch it and merge it. See also git-pull(1).

           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, 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.

           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.

           To reapply a series of changes from a branch to a different base, and reset the head
           of that branch to the result.

           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.

           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.

           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.

           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.

           The action of fixing up manually what a failed automatic merge left behind.

           Synonym for commit (the noun).

           To throw away part of the development, i.e. to assign the head to an earlier revision.

           Source code management (tool).

           "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.

           A repository that holds the history of a separate project inside another repository
           (the latter of which is called 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.

           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.

           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.

           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

           A repository can have zero (i.e. bare repository) or one or more worktrees attached to
           it. One "worktree" consists of a "working tree" and repository metadata, most of which
           are shared among other worktrees of a single repository, and some of which are
           maintained separately per worktree (e.g. the index, HEAD and pseudorefs like
           MERGE_HEAD, per-worktree refs and per-worktree configuration file).


       gittutorial(7), gittutorial-2(7), gitcvs-migration(7), giteveryday(7), The Git User’s


       Part of the git(1) suite


        1. The Git User’s Manual