How can I make autocomplete in the shell work with case-folding? How can I make the autocompletion for files and folders in the bash shell work case-insensitively?

Ideally, cd ~/doc + tab autocompletes to cd ~/Documents (correcting the case as it autocompletes), but if that's not possible autocompleting to cd ~/documents is acceptable too.
You can do that by typing the following command in the terminal:

echo 'set completion-ignore-case On' &gt;&gt; ~/.inputrc


if you want to go back to the original behavior you have the open that file and remove the line.

The file ~/.inputrc file deals with mapping the keyboard for specific situations. This file is the start-up file used by Readline, the input-related library used by Bash, perl and most other open source programs. 


  The configuration options in .inputrc are particularly useful for
  customising the way Tab-completion works, e.g. with the ls command
  
  When a program which uses the Readline library starts up, the init
  file is read, and the key bindings are set.


You can find more information about the file syntax in "Bash startup files".