Improper handling of whitespace-only lines with markEmptyLines set to true

[MrMino]

The colors in the diff are either not showing up, or are completely wrong / misleading.

Repro steps:

git config --bool --global diff-so-fancy.markEmptyLines true

cd $(mktemp -d)
git init
git commit --allow-empty -m "Initial commit"
echo -en "----\n\n----\n" > file
git add file; git commit -m "Add file"

# Shows empty lines properly
git show

# But then shows two lines deleted here
echo -en "----\n    \n----\n" > file
git diff

git add file

# Then, after removing one space, it looks as if 3 spaces were removed from a line below a blank one
echo -en "----\n   \n----\n" > file
git diff

git add file

# Then, after removing all of the whitespace, it now looks as if a blank line was added,
# and the file now contains 2 blank lines, where in reality it contains 1
echo -en "----\n\n----\n" > file
git diff

This makes removing redundant whitespace from blank lines, common in older Python codebases, painful.

[x-yuri]

Not sure if it's a different issue or not, but my case is:

a.sh

# rm -rf b
mkdir b
cd b
git init

# create a file with a space on a second line
echo 'a
 
b' > f
git add f
git commit -m a

# remove the space
echo 'a

b' > f
sed -Ei 's/ //' f
git diff

$ sh -eu a.sh

The way it looks like with diff-so-fancy:

Without:

markEmptyLines doesn't affect it.

I'd say it looks like a line was added, instead of a line was stripped of spaces.