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diff --git a/Documentation/glossary.txt b/Documentation/glossary.txt new file mode 100644 index 0000000..02a9d9c --- /dev/null +++ b/Documentation/glossary.txt @@ -0,0 +1,253 @@ +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 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). + +SHA1:: + Synonym for object name. + +object identifier:: + Synonym for object name. + +hash:: + In git's context, synonym to object name. + +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/`. + +blob object:: + Untyped object, e.g. the contents of a file. + +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:: + 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). + +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). + +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). + +unmerged index: + An index which contains unmerged index entries. + +cache:: + Obsolete for: index. + +working tree:: + The set of files and directories currently being worked on, + i.e. you can work in your working tree without using git at all. + +directory:: + The list you get with "ls" :-) + +revision:: + A particular state of files and directories which was stored in + the object database. It is referenced by a commit object. + +checkout:: + The action of updating the working tree to a revision which was + stored in the object database. + +commit:: + As a verb: The action of storing the current state of the index in the + object database. The result is a revision. + As a noun: Short hand for commit object. + +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. + +parent:: + A commit object contains a (possibly empty) list of the logical + predecessor(s) in the line of development, i.e. 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. + +clean:: + A working tree is clean, if it corresponds to the revision + referenced by the current head. + +dirty:: + A working tree is said to be dirty if it contains modifications + which have not been committed to the current branch. + +head:: + The top of a branch. It contains a ref to the corresponding + commit object. + +branch:: + A non-cyclical graph of revisions, i.e. the complete history of + a particular revision, which is called the branch head. The + branch heads are stored in `$GIT_DIR/refs/heads/`. + +master:: + The default 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. + +origin:: + The default upstream branch. Most projects have one upstream + project which they track, and by default 'origin' is used for + that purpose. New updates from upstream will be fetched into + this branch; you should never commit to it yourself. + +ref:: + A 40-byte hex representation of a SHA1 pointing to a particular + object. These may be stored in `$GIT_DIR/refs/`. + +head ref:: + A ref pointing to a head. Often, this is abbreviated to "head". + Head refs are stored in `$GIT_DIR/refs/heads/`. + +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. + +ent:: + Favorite synonym to "tree-ish" by some total geeks. See + `http://en.wikipedia.org/wiki/Ent_(Middle-earth)` for an in-depth + explanation. + +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". + +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 is called object type in git's context). + A tag is most typically used to mark a particular point in the + commit ancestry chain. + +merge:: + To merge branches means to try to accumulate the changes since a + common ancestor and apply them to the first branch. An automatic + merge uses heuristics to accomplish that. Evidently, an automatic + merge can fail. + +octopus:: + To merge more than two branches. Also denotes an intelligent + predator. + +resolve:: + The action of fixing up manually what a failed automatic merge + left behind. + +rewind:: + To throw away part of the development, i.e. to assign the head to + an earlier revision. + +rebase:: + To clean a branch by starting from the head of the main line of + development ("master"), and reapply the (possibly cherry-picked) + changes from that branch. + +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. + +git archive:: + Synonym for repository (for arch people). + +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. + +alternate object database:: + Via the alternates mechanism, a repository can inherit part of its + object database from another object database, which is called + "alternate". + +reachable:: + An object is reachable from a ref/commit/tree/tag, if there is a + chain leading from the latter to the former. + +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). + +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. + +pull:: + Pulling a branch means to fetch it and merge it. + +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. + +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. + +core git:: + Fundamental data structures and utilities of git. Exposes only + limited source code management tools. + +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. + +object type: + One of the identifiers "commit","tree","tag" and "blob" describing + the type of an object. + +SCM:: + Source code management (tool). + +dircache:: + You are *waaaaay* behind. + |