Assert the entire lines using Equals instead of Contains. This makes the tests a
bit easier to read, and it makes it much easier to decide how they need to be
changed when we change the layout (like we do in the last commit of this
branch).
It is true that this requires changing all these tests for any future UI
changes, but I think this is a good price to pay; those adaptions are trivial
and can be done without thinking.
After discarding file changes from the commit, the was still referencing
these indexes as being part of the range select. The consequence was
needing to hit escape twice to exit commit files in some situations.
Canceling the range select after discarding changes fixes that.
I'm combining the delete single file case from `discard_old_file_change`
with the content of `discard_range_select` and calling that
`discard_old_file_changes`. Hopefully that cleans things up a little
bit.
This also adds a check that the custom patch is getting reset properly.
