Fix the prepare_branch function

Currently when checking if the destination branch already exists the
command 'git branch' is used. This only returns local branches. What is
actually required is the list of remote branches. This can be obtained
by the command 'git branch -r' and filtering the result.

Author: adbridge

tools/test/examples/update.py

@@ -268,10 +268,19 @@ def prepare_branch(src, dst):
     update_log.debug("Preparing branch: %s", dst)
 
     # Check if branch already exists or not.
-    cmd = ['git', 'branch']
+    # We can use the 'git branch -r' command. This returns all the remote branches for
+    # the current repo.
+    # The output consists of a list of lines of the form:
+    # origin/<branch>
+    # From these we need to extract just the branch names to a list and then check if 
+    # the specified dst exists in that list
+    branches = []
+    cmd = "git branch -r"
     _, output = run_cmd_with_output(cmd, exit_on_failure=True)
 
-    if not dst in output:
+    branches = [line.split('/')[1] for line in output.split('\n') if 'origin' in line and not '->' in line]
+  
+    if not dst in branches:
 
         # OOB branch does not exist thus create it, first ensuring we are on 
         # the src branch and then check it out