ag: add -l and -o options

pages/common/ag.md

@@ -2,13 +2,17 @@
 
 > The Silver Searcher. Like ack, but faster.
 
-- Find files containing "foo":
+- Find files containing "foo", and print the line matches in context:
 
 `ag foo`
 
-- Find files containing "FOO" case-insensitively:
+- Find files containing "foo", but only list the filenames:
 
-`ag -i FOO`
+`ag -l foo`
+
+- Find files containing "FOO" case-insensitively, and print only the match, rather than the whole line:
+
+`ag -i -o FOO`
 
 - Find "foo" in files with a name matching "bar":