doc: documentation update for the branch track changes

Documents the branch.autosetupmerge=always setting and usage of --track
when branching from a local branch.
Signed-off-by: NJay Soffian <jaysoffian@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -330,10 +330,14 @@ apply.whitespace::
 
 branch.autosetupmerge::
 	Tells `git-branch` and `git-checkout` to setup new branches
-	so that linkgit:git-pull[1] will appropriately merge from that
-	remote branch.  Note that even if this option is not set,
+	so that linkgit:git-pull[1] will appropriately merge from the
+	starting point branch. Note that even if this option is not set,
 	this behavior can be chosen per-branch using the `--track`
-	and `--no-track` options.  This option defaults to false.
+	and `--no-track` options. The valid settings are: `false` -- no
+	automatic setup is done; `true` -- automatic setup is done when the
+	starting point is a remote branch; `always` -- automatic setup is
+	done when the starting point is either a local branch or remote
+	branch. This option defaults to true.
 
 branch.<name>.remote::
 	When in branch <name>, it tells `git fetch` which remote to fetch.

Documentation/git-branch.txt

@@ -34,12 +34,11 @@ Note that this will create the new branch, but it will not switch the
 working tree to it; use "git checkout <newbranch>" to switch to the
 new branch.
 
-When a local branch is started off a remote branch, git can setup the
-branch so that linkgit:git-pull[1] will appropriately merge from that
-remote branch.  If this behavior is desired, it is possible to make it
-the default using the global `branch.autosetupmerge` configuration
-flag.  Otherwise, it can be chosen per-branch using the `--track`
-and `--no-track` options.
+When a local branch is started off a remote branch, git sets up the
+branch so that linkgit:git-pull[1] will appropriately merge from
+the remote branch. This behavior may be changed via the global
+`branch.autosetupmerge` configuration flag. That setting can be
+overridden by using the `--track` and `--no-track` options.
 
 With a '-m' or '-M' option, <oldbranch> will be renamed to <newbranch>.
 If <oldbranch> had a corresponding reflog, it is renamed to match
@@ -105,19 +104,19 @@ OPTIONS
 	Display the full sha1s in output listing rather than abbreviating them.
 
 --track::
-	Set up configuration so that git-pull will automatically
-	retrieve data from the remote branch.  Use this if you always
-	pull from the same remote branch into the new branch, or if you
-	don't want to use "git pull <repository> <refspec>" explicitly.  Set the
-	branch.autosetupmerge configuration variable to true if you
-	want git-checkout and git-branch to always behave as if
-	'--track' were given.
+	When creating a new branch, set up configuration so that git-pull
+	will automatically retrieve data from the start point, which must be
+	a branch. Use this if you always pull from the same upstream branch
+	into the new branch, and if you don't want to use "git pull
+	<repository> <refspec>" explicitly. This behavior is the default
+	when the start point is a remote branch. Set the
+	branch.autosetupmerge configuration variable to `false` if you want
+	git-checkout and git-branch to always behave as if '--no-track' were
+	given. Set it to `always` if you want this behavior when the
+	start-point is either a local or remote branch.
 
 --no-track::
-	When a branch is created off a remote branch,
-	set up configuration so that git-pull will not retrieve data
-	from the remote branch, ignoring the branch.autosetupmerge
-	configuration variable.
+	Ignore the branch.autosetupmerge configuration variable.
 
 <branchname>::
 	The name of the branch to create or delete.

Documentation/git-checkout.txt

@@ -48,20 +48,19 @@ OPTIONS
 	may restrict the characters allowed in a branch name.
 
 --track::
-	When -b is given and a branch is created off a remote branch,
-	set up configuration so that git-pull will automatically
-	retrieve data from the remote branch.  Use this if you always
-	pull from the same remote branch into the new branch, or if you
-	don't want to use "git pull <repository> <refspec>" explicitly.  Set the
-	branch.autosetupmerge configuration variable to true if you
-	want git-checkout and git-branch to always behave as if
-	'--track' were given.
+	When creating a new branch, set up configuration so that git-pull
+	will automatically retrieve data from the start point, which must be
+	a branch. Use this if you always pull from the same upstream branch
+	into the new branch, and if you don't want to use "git pull
+	<repository> <refspec>" explicitly. This behavior is the default
+	when the start point is a remote branch. Set the
+	branch.autosetupmerge configuration variable to `false` if you want
+	git-checkout and git-branch to always behave as if '--no-track' were
+	given. Set it to `always` if you want this behavior when the
+	start-point is either a local or remote branch.
 
 --no-track::
-	When -b is given and a branch is created off a remote branch,
-	set up configuration so that git-pull will not retrieve data
-	from the remote branch, ignoring the branch.autosetupmerge
-	configuration variable.
+	Ignore the branch.autosetupmerge configuration variable.
 
 -l::
 	Create the new branch's reflog.  This activates recording of