This list is sorted alphabetically:
Via the alternates mechanism, a repository can inherit part of its object database from another object database, which is called "alternate".
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.
Untyped object, e.g. the contents of a file.
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/.
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 the working tree to a revision which was stored in the object database.
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 different codebase. In GIT, this is performed by "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 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.
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.
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).
You are waaaaay behind.
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.
Favorite synonym to "tree-ish" by some total geeks. See http://en.wikipedia.org/wiki/Ent_(Middle-earth) for an in-depth explanation.
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 these cases, you do not make a new merge commit but instead just update to his revision. This will happen frequently on a 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.
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.
Synonym for repository (for arch people).
In git's context, synonym to object name.
The top of a branch. It contains a ref to the corresponding commit object.
A ref pointing to a head. Often, this is abbreviated to "head". Head refs are stored in $GIT_DIR/refs/heads/.
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.
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.
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 conventional and not required.
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.
The unit of storage in git. It is uniquely identified by the SHA1 of its contents. Consequently, an object can not be changed.
Stores a set of "objects", and an individual object is identified by its object name. The objects usually live in $GIT_DIR/objects/.
Synonym for 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).
To merge more than two branches. Also denotes an intelligent predator.
The default upstream tracking branch. 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 this branch; you should never commit to it yourself.
A set of objects which have been compressed into one file (to save space or to transmit them efficiently).
The list of identifiers, and other information, of the objects in a pack, to assist in efficiently accessing the contents of a pack.
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.
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.
An object is reachable from a ref/commit/tree/tag, if there is a chain leading from the latter to the former.
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.
A 40-byte hex representation of a SHA1 or a name that denotes a particular object. These may be stored in $GIT_DIR/refs/.
A refspec is used by fetch and push to describe the mapping between remote ref and local ref. They are combined with a colon in the format <src>:<dst>, preceded by an optional plus sign, +. For example: git fetch $URL refs/heads/master:refs/heads/origin means "grab the master branch head 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 master head at $URL". See also git-push(1)
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.
The action of fixing up manually what a failed automatic merge left behind.
A particular state of files and directories which was stored in the object database. It is referenced by a commit object.
To throw away part of the development, i.e. to assign the head to an earlier revision.
Source code management (tool).
Synonym for object name.
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.
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".
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.
A regular git branch that is used to follow changes from another repository. 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 ref in a Pull: refspec.
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).
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.
A ref pointing to either a commit object, a tree object, or a tag object pointing to a tag or commit or tree object.
The set of files and directories currently being worked on, i.e. you can work in your working tree without using git at all.
Written by Johannes Schindelin <Johannes.Schindelin@gmx.de> and the git-list <git@vger.kernel.org>.
Part of the git suite