++
+When used in `git-push`, the <src> side can be an
+arbitrary "SHA1 expression" that can be used as an
+argument to `git-cat-file -t`. E.g. `master~4` (push
+four parents before the current master head).
++
+For `git-push`, the local ref that matches <src> is used
+to fast forward the remote ref that matches <dst>. If
+the optional plus `+` is used, the remote ref is updated
+even if it does not result in a fast forward update.
++
+For `git-fetch` and `git-pull`, the remote ref that matches <src>
+is fetched, and if <dst> is not empty string, the local
+ref that matches it is fast forwarded using <src>.
+Again, if the optional plus `+` is used, the local ref
+is updated even if it does not result in a fast forward
+update.
++
+[NOTE]
+If the remote branch from which you want to pull is
+modified in non-linear ways such as being rewound and
+rebased frequently, then a pull will attempt a merge with
+an older version of itself, likely conflict, and fail.
+It is under these conditions that you would want to use
+the `+` sign to indicate non-fast-forward updates will
+be needed. There is currently no easy way to determine
+or declare that a branch will be made available in a
+repository with this behavior; the pulling user simply
+must know this is the expected usage pattern for a branch.
++
+[NOTE]
+You never do your own development on branches that appear
+on the right hand side of a <refspec> colon on `Pull:` lines;
+they are to be updated by `git-fetch`. The corollary is that
+a local branch should be introduced and named on a <refspec>
+right-hand-side if you intend to do development derived from
+that branch.
+This leads to the common `Pull: master:origin` mapping of a
+remote `master` branch to a local `origin` branch, which
+is then merged to a local development branch, again typically
+named `master`.
++
+Some short-cut notations are also supported.
++
+* For backward compatibility, `tag` is almost ignored;
+ it just makes the following parameter <tag> to mean a
+ refspec `refs/tags/<tag>:refs/tags/<tag>`.
+* A parameter <ref> without a colon is equivalent to
+ <ref>: when pulling/fetching, and <ref>`:`<ref> when
+ pushing. That is, do not store it locally if
+ fetching, and update the same name if pushing.