Diff editor shows that (almost) entire file has changed when it's not

[alekseyt]

Issue Type: Bug

Doesn't always reproduce, but i've found a file where it bugs out.

Steps to reproduce:

1. Create a new Git repo: git init
2. Commit file from https://unicode.org/Public/UCA/11.0.0/allkeys.txt
3. Replace the same file with version 12.0.0: https://unicode.org/Public/UCA/12.0.0/allkeys.txt
4. Open directory with this Git repo in vscode ("File: Open Folder")
5. In sidebar select "Source control" and open diff editor

Result:

6. Execute git diff in terminal (or Git Bash)

IMO output of git diff is more informative about what changes were made to this file between versions.

I've seen diff results like that before on other files (actual source code).

I've also prepared Git repository where issue reproduces so steps 1-3 can be skipped: repro.zip

VS Code version: Code 1.29.1 (bc24f98b5f70467bc689abf41cc5550ca637088e, 2018-11-15T19:07:43.495Z) OS version: Linux x64 4.4.0-142-generic

Extensions (5)

Extension|Author (truncated)|Version ---|---|--- cpptools|ms-|0.19.0 shader|sle|1.1.4 vscode-lua|tri|0.12.4 cmake|twx|0.0.17 vscode-todo-highlight|way|1.0.4 (1 theme extensions excluded)

[vscodebot[bot]]

(Experimental duplicate detection) Thanks for submitting this issue. Please also check if it is already covered by an existing one, like:

• Code detects repositories when used as a difftool in Git Bash (#55428)

[alexdima]

I have added diffEditor.maxComputationTime and there is now a click widget that appears when the diff algorithm quits early.

To verify, download the .zip and open the diff. If the maximum computation time is reached, a widget is shown which helps with increasing the timeout.

[alexdima]

After discussions in standup, there is no click widget, but a notification when the diff computation times out.