Reproduction steps
echo foo > a.txt && echo bar > b.txt
git add . && git commit -m temp
rm a.txt && chmod +x b.txt
git diff
Output:

a.txt's output is being displayed after the mode change of b.txt
Raw git output:
diff --git a/a.txt b/a.txt
deleted file mode 100644
index 257cc56..0000000
--- a/a.txt
+++ /dev/null
@@ -1 +0,0 @@
-foo
diff --git a/b.txt b/b.txt
old mode 100644
new mode 100755
Delta's config:
commit-style = raw
file-style = blue
hunk-header-style = syntax
minus-style = normal "#3f0001"
minus-non-emph-style = normal "#3f0001"
minus-emph-style = normal "#901011"
minus-empty-line-marker-style = normal "#3f0001"
zero-style = syntax
plus-style = syntax "#002800"
plus-non-emph-style = syntax "#002800"
plus-emph-style = syntax "#006000"
plus-empty-line-marker-style = normal "#002800"
grep-file-style = purple
grep-line-number-style = green
whitespace-error-style = reverse purple
blame-palette = #000000 #222222 #444444
true-color = true
file-added-label = 'added:'
file-modified-label = ''
file-removed-label = 'removed:'
file-renamed-label = 'renamed:'
right-arrow = '⟶ '
hyperlinks = false
inspect-raw-lines = true
keep-plus-minus-markers = false
line-numbers = false
max-line-distance = 0.6
max-line-length = 512
diff-stat-align-width = 48
line-fill-method = ansi
navigate = false
navigate-regex =
pager = none
paging = auto
side-by-side = false
syntax-theme = Monokai Extended
width = 163
tabs = 8
word-diff-regex = '\w+'
Reproduction steps
Output:

a.txt's output is being displayed after the mode change ofb.txtRaw git output:
Delta's config: