We make the name of the GetSelectedRefRangeForDiffFiles very specific on purpose
to make it clear that this is only for switching to diff files, so the
implementations can make assumptions about that (unlike GetSelectedRef, which is
used for different purposes and needs to stay more generic).
Several custom patch commands on parts of an added file would fail with the
confusing error message "error: new file XXX depends on old contents". These
were dropping the custom patch from the original commit, moving the patch to a
new commit, moving it to a later commit, or moving it to the index.
We fix this by converting the patch header from an added file to a diff against
an empty file. We do this not just for the purpose of applying the patch, but
also for rendering it and copying it to the clip board. I'm not sure it matters
much in these cases, but it does feel more correct for a filtered patch to be
presented this way.
We're going to add another argument in the next commit, and that's getting a bit
much, especially when most of the arguments are bool and you only see true and
false at the call sites without knowing what they mean.
It's not possible to reliably stage things into a custom patch when "ignore
whitespace" is on, so always treat it as off here (like we do in the staging
panel).
It looks like this is a regression that was introduced in 8edad826ca.
This begins a big refactor of moving more code out of the Gui struct into contexts, controllers, and helpers. We also move some code into structs in the
gui package purely for the sake of better encapsulation
