Add git_update_remote_branch to functions.

When $RECLONE=yes, and the branch specified for a project in stackrc is
a remote branch, the git_clone function would not recognize it as a
branch.  git_clone now attempts to recognize a remote branch and handle
it appropriately.

Change-Id: Ie23ff12eb5a7905088a9c2bb0ea2b02453ec0258

AUTHORS

@@ -1,6 +1,7 @@
 Aaron Lee <aaron.lee@rackspace.com>
 Aaron Rosen <arosen@nicira.com>
 Adam Gandelman <adamg@canonical.com>
+Andrew Laski <andrew.laski@rackspace.com>
 Andy Smith <github@anarkystic.com>
 Anthony Young <sleepsonthefloor@gmail.com>
 Armando Migliaccio <armando.migliaccio@eu.citrix.com>

functions

@@ -278,6 +278,16 @@ function git_update_tag() {
 }
 
 
+# git update using reference as a branch.
+# git_update_remote_branch ref
+function git_update_remote_branch() {
+
+    GIT_BRANCH=$1
+
+    git checkout -b $GIT_BRANCH -t origin/$GIT_BRANCH
+}
+
+
 # Translate the OS version values into common nomenclature
 # Sets ``DISTRO`` from the ``os_*`` values
 function GetDistro() {
@@ -343,6 +353,8 @@ function git_clone {
                 git_update_tag $GIT_REF
             elif [[ -n "`git show-ref refs/heads/$GIT_REF`" ]]; then
                 git_update_branch $GIT_REF
+            elif [[ -n "`git show-ref refs/remotes/origin/$GIT_REF`" ]]; then
+                git_update_remote_branch $GIT_REF
             else
                 echo $GIT_REF is neither branch nor tag
                 exit 1