Rename of file is causing changes to be lost

[Robert Dailey <rcdailey.lists@gmail.com>]

I'm on Windows and core.ignorecase is set to 'true' when I clone/init
a repository. I've got a branch where I started making changes to a
file AND renamed it only to change its case. The changes I've made
were significant enough that git no longer detects a rename, instead
the files show up as "D" and "A" in git status (deleted then added).
To correct this, I do an interactive rebase to add an additional
commit before the first one to rename the file without changing it,
and *then* allow the second commit to change the file. The goal is
that rebase should detect the rename and automatically move the
changes in the (now) second commit to the newly named file. Here's a
MCVE (treat this as a script):

#/bin/bash
git init testgitrepo
cd testgitrepo/
git config core.ignorecase true # This is set by Windows for me, but
hopefully will allow this to repro on linux. Didn't test linux though.
echo "first change" > foo.txt
git add . && git commit -m 'first change'
git checkout -b topic
echo "second change" > foo.txt
git mv foo.txt FOO.txt
git add . && git commit -m 'second change'
git rebase -i master # Move line 1 to line 2, and put "x false" in line 1
git mv foo.txt FOO.txt && git commit -m 'rename foo'
git rebase --continue
git mergetool

After the rebase continue, you will get a conflict like so:

error: could not apply 527d208... second change

When you have resolved this problem, run "git rebase --continue".
If you prefer to skip this patch, run "git rebase --skip" instead.
To check out the original branch and stop rebasing, run "git rebase --abort".

Could not apply 527d208... second change
CONFLICT (rename/delete): foo.txt deleted in 527d208... second change
and renamed to FOO.txt in HEAD. Version HEAD of FOO.txt left in tree.

The last command, `git mergetool` runs, giving you the option to pick
the Created (left) or Deleted (right) version of the file:

Left: The file is created, but selecting this erases the changes from
the "added" version on the remote (which is topic). Basically the
rename of only case confused git, and we lost the changes on the
remote version of the file
Right: File is deleted. Changes are still lost.

The ideal outcome is that the changes from the "added" version of the
file in the 2nd commit get carried over to the "renamed" version of
the file, which when you compare the two are named exactly the same
after the 1st commit is introduced. How can I solve this issue?