+SHA1::
+ Synonym for object name.
+
+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.
+
+tracking branch::
+ 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.
+
+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).
+
+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.
+
+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.
+
+unmerged index:
+ An index which contains unmerged index entries.
+
+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.