Problem with Branches with "+" in them and Feature Branches -> Compare page link. (BB-8683)

I believe that I may have identified a bug in the link between the "Commits" page and the "Compare" page.

Symptoms/Reproduction

• My repository has a branch with a "" symbol in it - specifically, at the end of the branch name - e.g. "TestBranch".
• Open "Feature Branches" (through "Commits", then "Feature Branches")
• Find feature branch, click "Compare"
• Browser is redirected to a URL for the compare function that has a "+" symbol at the end, rather than the URL encoded "%2B".
• Browser displays page that states:
  "need more than 1 value to unpack"

Expected Result

• User is taken to "Compare" page.
• URL is encoded properly.