Automatically compare to a default branch after clicking the 'compare' tab

Description

Automatically compare to a default branch after clicking the 'compare' tab. Currently, the user needs to click compare first before anything is shown.

Proposal

When the repository > compare tab is selected for a particular branch, automatically compare with the default branch to show commits and file changes.

Links / references

Documentation blurb

Automatically compare to a default branch:

1. Selecting the comparison tab doesn't show a branch comparison until the user clicks compare.
2. Automatically show the comparison with the default branch when the branch is selected.