git/Documentation/pull-fetch-param.txt

<repository>::
	The "remote" repository that is the source of a fetch
	or pull operation.  This parameter can be either a URL
	(see the section <<URLS,GIT URLS>> below) or the name
	of a remote (see the section <<REMOTES,REMOTES>> below).

ifndef::git-pull[]
<group>::
	A name referring to a list of repositories as the value
	of remotes.<group> in the configuration file.
	(See linkgit:git-config[1]).
endif::git-pull[]

<refspec>::
	The format of a <refspec> parameter is an optional plus
	`+`, followed by the source ref <src>, followed
	by a colon `:`, followed by the destination ref <dst>.
+
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>.
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'.  If you intend to do
development derived from a remote branch `B`, have a `Pull:`
line to track it (i.e. `Pull: B:remote-B`), and have a separate
branch `my-B` to do your development on top of it.  The latter
is created by `git branch my-B remote-B` (or its equivalent `git
checkout -b my-B remote-B`).  Run `git fetch` to keep track of
the progress of the remote side, and when you see something new
on the remote branch, merge it into your development branch with
`git pull . remote-B`, while you are on `my-B` branch.
+
[NOTE]
There is a difference between listing multiple <refspec>
directly on 'git pull' command line and having multiple
`Pull:` <refspec> lines for a <repository> and running
'git pull' command without any explicit <refspec> parameters.
<refspec> listed explicitly on the command line are always
merged into the current branch after fetching.  In other words,
if you list more than one remote refs, you would be making
an Octopus.  While 'git pull' run without any explicit <refspec>
parameter takes default <refspec>s from `Pull:` lines, it
merges only the first <refspec> found into the current branch,
after fetching all the remote refs.  This is because making an
Octopus from remote refs is rarely done, while keeping track
of multiple remote heads in one-go by fetching more than one
is often useful.
+
Some short-cut notations are also supported.
+
* `tag <tag>` means the same as `refs/tags/<tag>:refs/tags/<tag>`;
  it requests fetching everything up to the given tag.
ifndef::git-pull[]
* A parameter <ref> without a colon fetches that ref into FETCH_HEAD,
endif::git-pull[]
ifdef::git-pull[]
* A parameter <ref> without a colon merges <ref> into the current
  branch,
endif::git-pull[]
  and updates the remote-tracking branches (if any).