Trim leading whitespace when copying to clipboard

[gabebw]

When copying deeply indented lines to the clipboard, I'd like all space up to the least-indented line to be trimmed (like strip_heredoc in Rails).

The kana/vim-textobj-line plugin does this for the il motion on a single line, but I want a visual-mode mapping so I can select lines, type cpil, and have it automagically left-aligned for me.