Kind-of-terrible (?) oncopy handler

Summary: Works in Safari, Firefox, Chrome.

Test Plan: Copied some text, threw up a little in my mouth.

Reviewers: aran, tuomaspelkonen, tomo, rstout, btrahan

Reviewed By: aran

CC: aran, epriestley, ddfisher

Maniphest Tasks: T145, T995

Differential Revision: https://secure.phabricator.com/D244

src/applications/differential/parser/changeset/DifferentialChangesetParser.php

@@ -1417,7 +1417,10 @@ final class DifferentialChangesetParser {
           '<th'.$o_id.'>'.$o_num.'</th>'.
           '<td'.$o_attr.'>'.$o_text.'</td>'.
           '<th'.$n_id.'>'.$n_num.'</th>'.
-          '<td'.$n_attr.'>'.$n_text.'</td>'.
+          // NOTE: This is a unicode zero-width space, which we use as a hint
+          // when intercepting 'copy' events to make sure sensible text ends
+          // up on the clipboard. See the 'phabricator-oncopy' behavior.
+          '<td'.$n_attr.'>'."\xE2\x80\x8B".$n_text.'</td>'.
           $n_cov.
         '</tr>';