# Glossary

Ancestor
  Any changeset that can be reached by an unbroken chain of parent changesets from a given changeset. More precisely, the ancestors of a changeset can be defined by two properties: a parent of a changeset is an ancestor, and a parent of an ancestor is an ancestor. See also: 'Descendant'.
Bookmark

  Bookmarks are pointers to certain commits that move when committing. They are similar to tags in that it is possible to use bookmark names in all places where Mercurial expects a changeset ID, e.g., with `hg update`. Unlike tags, bookmarks move along when you make a commit.

  Bookmarks can be renamed, copied and deleted. Bookmarks are local, unless they are explicitly pushed or pulled between repositories. Pushing and pulling bookmarks allow you to collaborate with others on a branch without creating a named branch.

Branch

  (Noun) A child changeset that has been created from a parent that is not a head. These are known as topological branches, see 'Branch, topological'. If a topological branch is named, it becomes a named branch. If a topological branch is not named, it becomes an anonymous branch. See 'Branch, anonymous' and 'Branch, named'.

  Branches may be created when changes are pulled from or pushed to a remote repository, since new heads may be created by these operations. Note that the term branch can also be used informally to describe a development process in which certain development is done independently of other development. This is sometimes done explicitly with a named branch, but it can also be done locally, using bookmarks or clones and anonymous branches.

  Example: "The experimental branch."

  (Verb) The action of creating a child changeset which results in its parent having more than one child.

  Example: "I'm going to branch at X."

Branch, anonymous
  Every time a new child changeset is created from a parent that is not a head and the name of the branch is not changed, a new anonymous branch is created.
Branch, closed
  A named branch whose branch heads have all been closed.
Branch, default
  The branch assigned to a changeset when no name has previously been assigned.
Branch head
  See 'Head, branch'.
Branch, inactive

  If a named branch has no topological heads, it is considered to be inactive. As an example, a feature branch becomes inactive when it is merged into the default branch. The `hg branches` command shows inactive branches by default, though they can be hidden with `hg branches --active`.

  NOTE: this concept is deprecated because it is too implicit. Branches should now be explicitly closed using `hg commit --close-branch` when they are no longer needed.

Branch, named

  A collection of changesets which have the same branch name. By default, children of a changeset in a named branch belong to the same named branch. A child can be explicitly assigned to a different branch. See `hg help branch`, `hg help branches` and `hg commit --close-branch` for more information on managing branches.

  Named branches can be thought of as a kind of namespace, dividing the collection of changesets that comprise the repository into a collection of disjoint subsets. A named branch is not necessarily a topological branch. If a new named branch is created from the head of another named branch, or the default branch, but no further changesets are added to that previous branch, then that previous branch will be a branch in name only.

Branch tip
  See 'Tip, branch'.
Branch, topological
  Every time a new child changeset is created from a parent that is not a head, a new topological branch is created. If a topological branch is named, it becomes a named branch. If a topological branch is not named, it becomes an anonymous branch of the current, possibly default, branch.
Changelog
  A record of the changesets in the order in which they were added to the repository. This includes details such as changeset id, author, commit message, date, and list of changed files.
Changeset
  A snapshot of the state of the repository used to record a change.
Changeset, child
  The converse of parent changeset: if P is a parent of C, then C is a child of P. There is no limit to the number of children that a changeset may have.
Changeset id
  A SHA-1 hash that uniquely identifies a changeset. It may be represented as either a "long" 40 hexadecimal digit string, or a "short" 12 hexadecimal digit string.
Changeset, merge
  A changeset with two parents. This occurs when a merge is committed.
Changeset, parent
  A revision upon which a child changeset is based. Specifically, a parent changeset of a changeset C is a changeset whose node immediately precedes C in the DAG. Changesets have at most two parents.
Checkout

  (Noun) The working directory being updated to a specific revision. This use should probably be avoided where possible, as changeset is much more appropriate than checkout in this context.

  Example: "I'm using checkout X."

  (Verb) Updating the working directory to a specific changeset. See `hg help update`.

  Example: "I'm going to check out changeset X."

Child changeset
  See 'Changeset, child'.
Close changeset
  See 'Head, closed branch'.
Closed branch
  See 'Branch, closed'.
Clone

  (Noun) An entire or partial copy of a repository. The partial clone must be in the form of a revision and its ancestors.

  Example: "Is your clone up to date?"

  (Verb) The process of creating a clone, using `hg clone`.

  Example: "I'm going to clone the repository."

Closed branch head
  See 'Head, closed branch'.
Commit

  (Noun) A synonym for changeset.

  Example: "Is the bug fixed in your recent commit?"

  (Verb) The act of recording changes to a repository. When files are committed in a working directory, Mercurial finds the differences between the committed files and their parent changeset, creating a new changeset in the repository.

  Example: "You should commit those changes now."

Cset
  A common abbreviation of the term changeset.
DAG
  The repository of changesets of a distributed version control system (DVCS) can be described as a directed acyclic graph (DAG), consisting of nodes and edges, where nodes correspond to changesets and edges imply a parent -> child relation. This graph can be visualized by graphical tools such as `hg log --graph`. In Mercurial, the DAG is limited by the requirement for children to have at most two parents.
Deprecated
  Feature removed from documentation, but not scheduled for removal.
Default branch
  See 'Branch, default'.
Descendant
  Any changeset that can be reached by a chain of child changesets from a given changeset. More precisely, the descendants of a changeset can be defined by two properties: the child of a changeset is a descendant, and the child of a descendant is a descendant. See also: 'Ancestor'.
Diff

  (Noun) The difference between the contents and attributes of files in two changesets or a changeset and the current working directory. The difference is usually represented in a standard form called a "diff" or "patch". The "git diff" format is used when the changes include copies, renames, or changes to file attributes, none of which can be represented/handled by classic "diff" and "patch".

  Example: "Did you see my correction in the diff?"

  (Verb) Diffing two changesets is the action of creating a diff or patch.

  Example: "If you diff with changeset X, you will see what I mean."

Directory, working
  The working directory represents the state of the files tracked by Mercurial, that will be recorded in the next commit. The working directory initially corresponds to the snapshot at an existing changeset, known as the parent of the working directory. See 'Parent, working directory'. The state may be modified by changes to the files introduced manually or by a merge. The repository metadata exists in the .hg directory inside the working directory.
Draft
  Changesets in the draft phase have not been shared with publishing repositories and may thus be safely changed by history-modifying extensions. See `hg help phases`.
Experimental
  Feature that may change or be removed at a later date.
Graph
  See DAG and `hg log --graph`.
Head

  The term 'head' may be used to refer to both a branch head or a repository head, depending on the context. See 'Head, branch' and 'Head, repository' for specific definitions.

  Heads are where development generally takes place and are the usual targets for update and merge operations.

Head, branch
  A changeset with no descendants on the same named branch.
Head, closed branch

  A changeset that marks a head as no longer interesting. The closed head is no longer listed by `hg heads`. A branch is considered closed when all its heads are closed and consequently is not listed by `hg branches`.

  Closed heads can be re-opened by committing new changeset as the child of the changeset that marks a head as closed.

Head, repository
  A topological head which has not been closed.
Head, topological
  A changeset with no children in the repository.
History, immutable
  Once committed, changesets cannot be altered. Extensions which appear to change history actually create new changesets that replace existing ones, and then destroy the old changesets. Doing so in public repositories can result in old changesets being reintroduced to the repository.
History, rewriting
  The changesets in a repository are immutable. However, extensions to Mercurial can be used to alter the repository, usually in such a way as to preserve changeset contents.
Immutable history
  See 'History, immutable'.
Merge changeset
  See 'Changeset, merge'.
Manifest
  Each changeset has a manifest, which is the list of files that are tracked by the changeset.
Merge
  Used to bring together divergent branches of work. When you update to a changeset and then merge another changeset, you bring the history of the latter changeset into your working directory. Once conflicts are resolved (and marked), this merge may be committed as a merge changeset, bringing two branches together in the DAG.
Named branch
  See 'Branch, named'.
Null changeset
  The empty changeset. It is the parent state of newly-initialized repositories and repositories with no checked out revision. It is thus the parent of root changesets and the effective ancestor when merging unrelated changesets. Can be specified by the alias 'null' or by the changeset ID '000000000000'.
Parent
  See 'Changeset, parent'.
Parent changeset
  See 'Changeset, parent'.
Parent, working directory
  The working directory parent reflects a virtual revision which is the child of the changeset (or two changesets with an uncommitted merge) shown by `hg parents`. This is changed with `hg update`. Other commands to see the working directory parent are `hg summary` and `hg id`. Can be specified by the alias ".".
Patch

  (Noun) The product of a diff operation.

  Example: "I've sent you my patch."

  (Verb) The process of using a patch file to transform one changeset into another.

  Example: "You will need to patch that revision."

Phase
  A per-changeset state tracking how the changeset has been or should be shared. See `hg help phases`.
Public
  Changesets in the public phase have been shared with publishing repositories and are therefore considered immutable. See `hg help phases`.
Pull
  An operation in which changesets in a remote repository which are not in the local repository are brought into the local repository. Note that this operation without special arguments only updates the repository, it does not update the files in the working directory. See `hg help pull`.
Push
  An operation in which changesets in a local repository which are not in a remote repository are sent to the remote repository. Note that this operation only adds changesets which have been committed locally to the remote repository. Uncommitted changes are not sent. See `hg help push`.
Repository
  The metadata describing all recorded states of a collection of files. Each recorded state is represented by a changeset. A repository is usually (but not always) found in the `.hg` subdirectory of a working directory. Any recorded state can be recreated by "updating" a working directory to a specific changeset.
Repository head
  See 'Head, repository'.
Revision
  A state of the repository at some point in time. Earlier revisions can be updated to by using `hg update`. See also 'Revision number'; See also 'Changeset'.
Revision number
  This integer uniquely identifies a changeset in a specific repository. It represents the order in which changesets were added to a repository, starting with revision number 0. Note that the revision number may be different in each clone of a repository. To identify changesets uniquely between different clones, see 'Changeset id'.
Revlog
  History storage mechanism used by Mercurial. It is a form of delta encoding, with occasional full revision of data followed by delta of each successive revision. It includes data and an index pointing to the data.
Rewriting history
  See 'History, rewriting'.
Root
  A changeset that has only the null changeset as its parent. Most repositories have only a single root changeset.
Secret
  Changesets in the secret phase may not be shared via push, pull, or clone. See `hg help phases`.
Tag
  An alternative name given to a changeset. Tags can be used in all places where Mercurial expects a changeset ID, e.g., with `hg update`. The creation of a tag is stored in the history and will thus automatically be shared with other using push and pull.
Tip
  The changeset with the highest revision number. It is the changeset most recently added in a repository.
Tip, branch
  The head of a given branch with the highest revision number. When a branch name is used as a revision identifier, it refers to the branch tip. See also 'Branch, head'. Note that because revision numbers may be different in different repository clones, the branch tip may be different in different cloned repositories.
Update

  (Noun) Another synonym of changeset.

  Example: "I've pushed an update."

  (Verb) This term is usually used to describe updating the state of the working directory to that of a specific changeset. See `hg help update`.

  Example: "You should update."

Working directory
  See 'Directory, working'.
Working directory parent
  See 'Parent, working directory'.