doc/checkout: split checkout and branch creation in synopsis

These can really be thought of as two different modes, since
the "<branch>" parameter is treated differently in the two
(in one it is the branch to be checked out, but in the other
it is really a start-point for branch creation).
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Documentation/git-checkout.txt

@@ -8,23 +8,22 @@ git-checkout - Checkout a branch or paths to the working tree
 SYNOPSIS
 --------
 [verse]
-'git checkout' [-q] [-f] [-m] [-b <new_branch>] [<branch>]
+'git checkout' [-q] [-f] [-m] [<branch>]
+'git checkout' [-q] [-f] [-m] [-b <new_branch>] [<start_point>]
 'git checkout' [-f|--ours|--theirs|-m|--conflict=<style>] [<tree-ish>] [--] <paths>...
 
 DESCRIPTION
 -----------
 
 When <paths> are not given, this command switches branches by
-updating the index and working tree to reflect the specified
-branch, <branch>, and updating HEAD to be <branch> or, if
-specified, <new_branch>.  Using -b will cause <new_branch> to
-be created as if linkgit:git-branch[1] were called; in this case you can
-use the --track or --no-track options, which will be passed to `git
-branch`.
+updating the index, working tree, and HEAD to reflect the specified
+branch.
 
-As a convenience, --track will default to creating a branch whose
-name is constructed from the specified branch name by stripping
-the first namespace level.
+If `-b` is given, a new branch is created and checked out, as if
+linkgit:git-branch[1] were called; in this case you can
+use the --track or --no-track options, which will be passed to `git
+branch`.  As a convenience, --track without `-b` implies branch
+creation; see the description of --track below.
 
 When <paths> are given, this command does *not* switch
 branches.  It updates the named paths in the working tree from
@@ -63,7 +62,7 @@ entries; instead, unmerged entries are ignored.
 
 -b::
 	Create a new branch named <new_branch> and start it at
-	<branch>; see linkgit:git-branch[1] for details.
+	<start_point>; see linkgit:git-branch[1] for details.
 
 -t::
 --track::
@@ -114,13 +113,6 @@ the conflicted merge in the specified paths.
 	"merge" (default) and "diff3" (in addition to what is shown by
 	"merge" style, shows the original contents).
 
-<new_branch>::
-	Name for the new branch.
-
-<tree-ish>::
-	Tree to checkout from (when paths are given). If not specified,
-	the index will be used.
-
 <branch>::
 	Branch to checkout (when no paths are given); may be any object
 	ID that resolves to a commit.  Defaults to HEAD.
@@ -132,6 +124,18 @@ As a special case, the `"@\{-N\}"` syntax for the N-th last branch
 checks out the branch (instead of detaching).  You may also specify
 `-` which is synonymous with `"@\{-1\}"`.
 
+<new_branch>::
+	Name for the new branch.
+
+<start_point>::
+	The name of a commit at which to start the new branch; see
+	linkgit:git-branch[1] for details. Defaults to HEAD.
+
+<tree-ish>::
+	Tree to checkout from (when paths are given). If not specified,
+	the index will be used.
+
+
 
 Detached HEAD
 -------------