GIT Glossary ============ [[def_alternate_object_database]]alternate object database:: Via the alternates mechanism, a <> can inherit part of its <> from another object database, which is called "alternate". [[def_bare_repository]]bare repository:: A bare repository is normally an appropriately named <> 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. [[def_blob_object]]blob object:: Untyped <>, e.g. the contents of a file. [[def_branch]]branch:: A "branch" is an active line of development. The most recent <> on a branch is referred to as the tip of that branch. The tip of the branch is referenced by a branch <>, which moves forward as additional development is done on the branch. A single git <> can track an arbitrary number of branches, but your <> is associated with just one of them (the "current" or "checked out" branch), and <> points to that branch. [[def_cache]]cache:: Obsolete for: <>. [[def_chain]]chain:: A list of objects, where each <> in the list contains a reference to its successor (for example, the successor of a <> could be one of its <>). [[def_changeset]]changeset:: BitKeeper/cvsps speak for "<>". Since git does not store changes, but states, it really does not make sense to use the term "changesets" with git. [[def_checkout]]checkout:: The action of updating the <> to a <> which was stored in the <>. [[def_cherry-picking]]cherry-picking:: In <> 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 <> and to record it based on the tip of the current <> as a new commit. [[def_clean]]clean:: A <> is clean, if it corresponds to the <> referenced by the current <>. Also see "<>". [[def_commit]]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 <>. + 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 <> and advancing <> to point at the new commit. [[def_commit_object]]commit object:: An <> which contains the information about a particular <>, such as <>, committer, author, date and the <> which corresponds to the top <> of the stored revision. [[def_core_git]]core git:: Fundamental data structures and utilities of git. Exposes only limited source code management tools. [[def_DAG]]DAG:: Directed acyclic graph. The <> objects form a directed acyclic graph, because they have parents (directed), and the graph of commit objects is acyclic (there is no <> which begins and ends with the same <>). [[def_dangling_object]]dangling object:: An <> which is not <> even from other unreachable objects; a dangling object has no references to it from any reference or <> in the <>. [[def_detached_HEAD]]detached HEAD:: Normally the <> stores the name of a <>. However, git also allows you to <> an arbitrary <> that isn't necessarily the tip of any particular branch. In this case HEAD is said to be "detached". [[def_dircache]]dircache:: You are *waaaaay* behind. See <>. [[def_directory]]directory:: The list you get with "ls" :-) [[def_dirty]]dirty:: A <> is said to be "dirty" if it contains modifications which have not been <> to the current <>. [[def_ent]]ent:: Favorite synonym to "<>" 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. [[def_evil_merge]]evil merge:: An evil merge is a <> that introduces changes that do not appear in any <>. [[def_fast_forward]]fast forward:: A fast-forward is a special type of <> where you have a <> and you are "merging" another <>'s changes that happen to be a descendant of what you have. In such these cases, you do not make a new <> <> but instead just update to his revision. This will happen frequently on a <> of a remote <>. [[def_fetch]]fetch:: Fetching a <> means to get the branch's <> from a remote <>, to find out which objects are missing from the local <>, and to get them, too. See also gitlink:git-fetch[1]. [[def_file_system]]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. [[def_git_archive]]git archive:: Synonym for <> (for arch people). [[def_grafts]]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 <> a <> has is different from what was recorded when the commit was created. Configured via the `.git/info/grafts` file. [[def_hash]]hash:: In git's context, synonym to <>. [[def_head]]head:: A <> to the <> at the tip of a <>. Heads are stored in `$GIT_DIR/refs/heads/`, except when using packed refs. (See gitlink:git-pack-refs[1].) [[def_HEAD]]HEAD:: The current <>. In more detail: Your <> is normally derived from the state of the tree referred to by HEAD. HEAD is a reference to one of the <> in your repository, except when using a <>, in which case it may reference an arbitrary commit. [[def_head_ref]]head ref:: A synonym for <>. [[def_hook]]hook:: During the normal execution of several git commands, call-outs are made to optional scripts that allow a developer to add functionality or checking. Typically, the hooks allow for a command to be pre-verified and potentially aborted, and allow for a post-notification after the operation is done. The hook scripts are found in the `$GIT_DIR/hooks/` directory, and are enabled by simply making them executable. [[def_index]]index:: A collection of files with stat information, whose contents are stored as objects. The index is a stored version of your <>. Truth be told, it can also contain a second, and even a third version of a working tree, which are used when <>. [[def_index_entry]]index entry:: The information regarding a particular file, stored in the <>. An index entry can be unmerged, if a <> was started, but not yet finished (i.e. if the index contains multiple versions of that file). [[def_master]]master:: The default development <>. Whenever you create a git <>, 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. [[def_merge]]merge:: As a verb: To bring the contents of another <> (possibly from an external <>) into the current branch. In the case where the merged-in branch is from a different repository, this is done by first <> the remote branch and then merging the result into the current branch. This combination of fetch and merge operations is called a <>. 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 <>, a successful merge results in the creation of a new <> representing the result of the merge, and having as <> the tips of the merged <>. This commit is referred to as a "merge commit", or sometimes just a "merge". [[def_object]]object:: The unit of storage in git. It is uniquely identified by the <> of its contents. Consequently, an object can not be changed. [[def_object_database]]object database:: Stores a set of "objects", and an individual <> is identified by its <>. The objects usually live in `$GIT_DIR/objects/`. [[def_object_identifier]]object identifier:: Synonym for <>. [[def_object_name]]object name:: The unique identifier of an <>. The <> of the object's contents using the Secure Hash Algorithm 1 and usually represented by the 40 character hexadecimal encoding of the <> of the object (possibly followed by a white space). [[def_object_type]]object type:: One of the identifiers "<>","<>","<>" or "<>" describing the type of an <>. [[def_octopus]]octopus:: To <> more than two <>. Also denotes an intelligent predator. [[def_origin]]origin:: The default upstream <>. 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 <> named origin/name-of-upstream-branch, which you can see using "`git branch -r`". [[def_pack]]pack:: A set of objects which have been compressed into one file (to save space or to transmit them efficiently). [[def_pack_index]]pack index:: The list of identifiers, and other information, of the objects in a <>, to assist in efficiently accessing the contents of a pack. [[def_parent]]parent:: A <> contains a (possibly empty) list of the logical predecessor(s) in the line of development, i.e. its parents. [[def_pickaxe]]pickaxe:: The term <> 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 <> that introduced or removed, say, a particular line of text. See gitlink:git-diff[1]. [[def_plumbing]]plumbing:: Cute name for <>. [[def_porcelain]]porcelain:: Cute name for programs and program suites depending on <>, presenting a high level access to core git. Porcelains expose more of a <> interface than the <>. [[def_pull]]pull:: Pulling a <> means to <> it and <> it. See also gitlink:git-pull[1]. [[def_push]]push:: Pushing a <> means to get the branch's <> from a remote <>, 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 <> from the local head ref, and which are missing from the remote repository, into the remote <>, and updating the remote head ref. If the remote <> is not an ancestor to the local head, the push fails. [[def_reachable]]reachable:: All of the ancestors of a given <> are said to be "reachable" from that commit. More generally, one <> is reachable from another if we can reach the one from the other by a <> that follows <> to whatever they tag, <> to their parents or trees, and <> to the trees or <> that they contain. [[def_rebase]]rebase:: To reapply a series of changes from a <> to a different base, and reset the <> of that branch to the result. [[def_ref]]ref:: A 40-byte hex representation of a <> or a name that denotes a particular <>. These may be stored in `$GIT_DIR/refs/`. [[def_refspec]]refspec:: A "refspec" is used by <> and <> to describe the mapping between remote <> and local ref. They are combined with a colon in the format :, preceded by an optional plus sign, +. For example: `git fetch $URL refs/heads/master:refs/heads/origin` means "grab the master <> <> 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 $URL". See also gitlink:git-push[1] [[def_repository]]repository:: A collection of <> together with an <> containing all objects which are <> from the refs, possibly accompanied by meta data from one or more <>. A repository can share an object database with other repositories via <>. [[def_resolve]]resolve:: The action of fixing up manually what a failed automatic <> left behind. [[def_revision]]revision:: A particular state of files and directories which was stored in the <>. It is referenced by a <>. [[def_rewind]]rewind:: To throw away part of the development, i.e. to assign the <> to an earlier <>. [[def_SCM]]SCM:: Source code management (tool). [[def_SHA1]]SHA1:: Synonym for <>. [[def_shallow_repository]]shallow repository:: A shallow <> has an incomplete history some of whose <> have <> cauterized away (in other words, git is told to pretend that these commits do not have the parents, even though they are recorded in the <>). This is sometimes useful when you are interested only in the recent history of a project even though the real history recorded in the upstream is much larger. A shallow repository is created by giving the `--depth` option to gitlink:git-clone[1], and its history can be later deepened with gitlink:git-fetch[1]. [[def_symref]]symref:: Symbolic reference: instead of containing the <> id itself, it is of the format 'ref: refs/some/thing' and when referenced, it recursively dereferences to this reference. '<>' is a prime example of a symref. Symbolic references are manipulated with the gitlink:git-symbolic-ref[1] command. [[def_tag]]tag:: A <> pointing to a <> or <>. In contrast to a <>, a tag is not changed by a <>. Tags (not <>) are stored in `$GIT_DIR/refs/tags/`. A git tag has nothing to do with a Lisp tag (which would be called an <> in git's context). A tag is most typically used to mark a particular point in the commit ancestry <>. [[def_tag_object]]tag object:: An <> containing a <> pointing to another object, which can contain a message just like a <>. It can also contain a (PGP) signature, in which case it is called a "signed tag object". [[def_topic_branch]]topic branch:: A regular git <> 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. [[def_tracking_branch]]tracking branch:: A regular git <> that is used to follow changes from another <>. 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 <> in a Pull: <>. [[def_tree]]tree:: Either a <>, or a <> together with the dependent <> and tree objects (i.e. a stored representation of a working tree). [[def_tree_object]]tree object:: An <> containing a list of file names and modes along with refs to the associated blob and/or tree objects. A <> is equivalent to a <>. [[def_tree-ish]]tree-ish:: A <> pointing to either a <>, a <>, or a <> pointing to a tag or commit or tree object. [[def_unmerged_index]]unmerged index:: An <> which contains unmerged <>. [[def_unreachable_object]]unreachable object:: An <> which is not <> from a <>, <>, or any other reference. [[def_working_tree]]working tree:: The tree of actual checked out files. The working tree is normally equal to the <> plus any local changes that you have made but not yet committed.