the_silver_searcher (grep-like text search, but faster)

Ag is a code searching tool similar to grep and ack, but with a focus
on speed.

Ag searches code about 3-5x faster than ack. It ignores file patterns
from your .gitignore and .hgignore. If there are files in your source
repo you don't want to search, just add their patterns to a .agignore
file. The command name is 33% shorter than ack!