save_indent_copy_syntax.user.js

// ==UserScript==
// @name        Save Indent - Better Copy for Github, Gist, google-code-prettify
// @namespace   https://gist.github.com/7cc
// @description save indent/whitespace when copy source code / コピーした際のインデントを正常化する
// @include     *
// @exclued     https://www.google*
// @exclued     https://www.youtube.com/*
// @version     2.03
// @grant       none
// ==/UserScript==

// works on
// github
// gist, gist-embed
// google-code-prettify wih line-break

// NOT works if the selection starts from an *un*highlighted element.  (= before code)

;(function(){


var syntaxType = ""
  if (location.host === "gist.github.com" || document.querySelector(".lines.highlight")) {
    syntaxType = "gist"
  }else if (location.host === "github.com") {
    syntaxType = "github"
  }else if (document.querySelector(".prettyprint.linenums")) {
    syntaxType = "google"
  }else {
    return
  }

var query = ({
  'gist': {
    body: ".blob-wrapper",
    line: '.line'
  },
  'github': {
    body: ".blob-wrapper",
    line:'.blob-line-code'
  },
  'google': {
    body: ".prettyprint *",
    line: 'li'
  }
}) [syntaxType]


document.addEventListener("copy", copySyntax, false)

function copySyntax(e) {
  var selectedNode = getSelection().anchorNode.nodetype === 1 ? getSelection().anchorNode : getSelection().anchorNode.parentNode
  var isSelectCode = selectedNode.matches(query.body + "," + query.body + " *")

  // disable if MarkDown
  if( selectedNode.matches(".markdown-body *") ) {
    return
  }

  if (isSelectCode) {
    var df = getSelection().getRangeAt(0).cloneContents()
      , td = df.querySelectorAll(query.line) // *
      , isOneLine =  td.length
      , copyTarget = isOneLine ? td : df.childNodes
      , joinStr = isOneLine ? "\n" : ""
      , copyDate

    copyDate = Array.map(copyTarget, function(e){
      return e.textContent.replace(/\n|^\u00A0$/gm, "")
    }).join(joinStr)
    //console.log(copyDate)

    e.clipboardData.setData("text/plain", copyDate)
    e.preventDefault()
  }
}


})()