Let’s say you want to update capybara and capybara-webkit. You’d normally type this:
gem update capybara capybara-webkit
But you’re busy, you don’t have time to type “capybara” twice. Let’s see what tab completion has for us:
gem update capybara{,-webkit}
The bracket expression expands to the same thing as abovebecause the brackets
expand to "capybara" + "" and "capybara" + "-webkit". If you’re in ZSH, you
can press the TAB key (gem update capybara{,-webkit}[TAB]) and it will expand
the expression for you inline. Bash users, this will still work for you, even
without the neat TAB trick.