What version are you running?
3.0.5
What's the URL of the page containing the problem?
https://rb.corp.linkedin.com/r/1768812/diff/4/ but it's not accessible from the outside.
What steps will reproduce the problem?

Make the following change to a .gitignore file:

diff --git a/.gitignore b/.gitignore
index 9fac507..99164ce 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,6 +16,7 @@
 .envrc
 .gradle/
 .idea/
+.shelf/
 .tox*
 .venv*
 /*/*pinned.txt
@@ -33,6 +34,7 @@
 /ligradle/
 TEST-*.xml
 __pycache__/
+.mypy_cache/


Commit locally and create a review-request
View the diff in ReviewBoard (see attached screenshot)


What is the expected output? What do you see instead?
Expected: a correctly-aligned diff

Actual:

- .tox on the right appears to be newly added (it is aligned with a non-line on the left hand side) even though .tox is also present on the left hand side

- a blank line is shown as newly-inserted even though it is also present on the left hand side
What operating system are you using? What browser?
client-side (from chrome://version/):
Google Chrome   74.0.3729.169 (Official Build) (64-bit)
Revision    78e4f8db3ce38f6c26cf56eed7ae9b331fc67ada-refs/branch-heads/3729@{#1013}
OS  Linux
JavaScript  V8 7.4.288.28
Flash   32.0.0.223 /home/aamyers/.config/google-chrome/PepperFlash/32.0.0.223/libpepflashplayer.so
User Agent  Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36
Command Line    /usr/bin/google-chrome-stable --flag-switches-begin --flag-switches-end
Executable Path /opt/google/chrome/google-chrome
Profile Path    /home/aamyers/.config/google-chrome/Profile 4


server-side:
$ uname -srvmpio
Linux 3.10.0-514.26.1.el7.x86_64 #1 SMP Tue Jun 20 01:16:02 EDT 2017 x86_64 x86_64 x86_64 GNU/Linux


Please provide any additional information below.