Fix logic error in main branch selection

I was previously looking at two different lists, `candidates` and
`branch_list`. So the numbers weren't matching up.

This is fixed now.

git-tidy

@@ -111,16 +111,17 @@ def get_default_branch() -> str:
 
     # If there's no clear default, let the user select which one to use:
     selection = -1
-    while (selection < 0) or (selection >= len(candidates)):
+    while (selection < 0) or (selection >= len(branch_list)):
         print("Unable to determine default branch automatically. Please select one:")
         for n, branch in enumerate(branch_list):
             print(f"{n}: {branch}")
 
-        raw_input = input("Which to choose?")
+        raw_input = input("Which to choose? ")
         try:
             selection = int(raw_input)
         except ValueError:
             continue
+        print(selection)
 
     return branch_list[selection]