Moving pages from one space to another with duplicate names in the page's children results in corrupt page hierarchy

When moving pages from one space to another, page names are not checked for conflicts. The copy appears to be successful, but then results in a corrupt page tree. There should be warnings for conflicting page names, and even better, and opportunity to rename the conflicting pages.

I was combining a large number of spaces into one today and didn't realize what was happening until I had at least 5 instances of a page named "Projects". Luckily I was doing this in a dev server.

To reproduce this issue:

Create 2 spaces, and select the "Documentation" theme for each:
1. Test A
2. Test B

In each space, rename the Home Page:
1. Test A > Home -> Test A > Test A Home
2. Test B > Home -> Test B > Test B Home

Create the following pages in each space under the home page:
1. Sub Page 1
2. Sub Page 2

The hierarchy should now be:
Space A:

• Space A Home
  • Sub Page 1
  • Sub Page 2

Space B:

• Space B Home
  • Sub Page 1
  • Sub Page 2

Navigate to Space B > Space B Home
From the "Tools" menu, select "Move"
Select "Browse"
Choose "Space A"
Click on "Space A Home"
Click "Move"

The page is moved.

The left nav shows the following hierarchy, in Space A:

• Sub Page 1
• Sub Page 2
  + Test B Home

Click the "+" next to Test B Home. The hierarchy shows:

• Sub Page 1
• Sub Page 2
• Test B Home
  • Sub Page 1
  • Sub Page 2

Obviously that's not good...

Now click on the first instance of Sub Page 1. The page loads and the hierarchy shows:

• Sub Page 1
• Sub Page 2
• Test B Home
  • Sub Page 1
  • Sub Page 2

Note that it is showing the second instance of Sub Page 1 selected, even though the first instance was clicked.