Checkout from -eol tag if stable branch does not exist

Since several projects stable/newton branches have been end of life'd,
we can't install base devstack on stable/newton.

This modifies the setup_workspace function to check, as a last resort,
if the base_branch is a stable branch and if there is a corresponding
-eol tag, to use that for the checkout rather than the stable branch.

This is needed in the cases that projects are end of life'd out of order,
as is the case with keystone, cinder and neutron being end of life before
nova for stable/newton.

Co-Authored-By: Eric Fried <efried@us.ibm.com>

Change-Id: I344d8fdded9b7d5385fcb41b699f1352acb4cda7

functions.sh

@@ -419,6 +419,12 @@ function setup_workspace {
             cd `basename $PROJECT`
             if git branch -a | grep "$base_branch" > /dev/null ; then
                 git checkout $base_branch
+            elif [[ "$base_branch" == stable/* ]]; then
+                # Look for an eol tag for the stable branch.
+                eol_tag=${base_branch#stable/}-eol
+                if [ $(git tag -l $eol_tag) ]; then
+                    git checkout -q $eol_tag
+                fi
             else
                 git checkout master
             fi