Find Commit That Introduced a String

# Find commits that added/removed the string "DEPRECATED_API"
git log -S "DEPRECATED_API" --pretty=format:'%h %ad %an  %s' --date=short

# Same but for a regex (-G instead of -S)
git log -G "deprecated.*api" --pretty=format:'%h %s' -i

# Restrict to a path
git log -S "TODO" -- src/

# Show the diff of the commit that introduced something
git log -S "function calculatePrice" -p

# `git blame` for the line-by-line author of a file
git blame src/payment.js -L 100,150