Copy WebKit Permalink may generate wrong URL with SVN checkout

Copy WebKit Permalink may generate wrong URL with SVN checkout
https://bugs.webkit.org/show_bug.cgi?id=176427

Reviewed by Darin Adler.

Fixes an issue where Copy WebKit Permalink would generate an incorrect URL for
any file not in the top-level directory of the repository when using an SVN
checkout of WebKit.

Copy WebKit Permalink changes directories to the containing directory D of the
active Xcode document F before running "svn info <path to F>". Currently we use
the value of "Path" from the output of "svn info" when generating the permalink.
This path is relative to D. But we want the path to F relative to the top-level
checkout directory. We need to explicitly compute this.

* CopyPermalink/Copy WebKit Permalink.workflow/Contents/document.wflow:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@221679 268f45cc-cd09-0410-ab3c-d52691b4dbfc