Slow git blame performance

Created by: alanhamlett

• Sourcegraph version: 2.11.0
• Platform: Search

Steps to reproduce:

1. view large file in Sourcegraph. For ex: a 597K Ruby file with 16653 lines
2. select a line, and notice the blame annotation takes a long time to load

Expected:

Blame should load in under a second

Actual:

Blame takes multiple seconds to load