[PATCH 1/4] Better error message when renaming patches to same name

Generate a more precise error message when trying to rename a patch to the
same name.  This is what we get currently:

  [cel@dexter main]$ stg rename nfs_direct_wait nfs_direct_wait
  Renaming patch "nfs_direct_wait" -> "nfs_direct_wait"...stg rename: Patch
  "nfs_direct_wait" already exists

  [cel@dexter main]$

Signed-off-by: Chuck Lever <redacted>
---

 stgit/stack.py |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/stgit/stack.py b/stgit/stack.py
index 1ffeaee..0907b37 100644
--- a/stgit/stack.py
+++ b/stgit/stack.py

@@ -775,6 +775,9 @@ class Series:
         applied = self.get_applied()
         unapplied = self.get_unapplied()
 
+        if oldname == newname:
+            raise StackException, '"To" name and "from" name are the same'
+
         if newname in applied or newname in unapplied:
             raise StackException, 'Patch "%s" already exists' % newname