[GHC] #10475: detabify User's Guide

[GHC]

#10475: detabify User's Guide
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              Reporter:  rwbarton    |             Owner:
                  Type:  task        |            Status:  new
              Priority:  low         |         Milestone:
             Component:              |           Version:  7.10.1
  Documentation                      |  Operating System:  Unknown/Multiple
              Keywords:              |   Type of failure:  None/Unknown
          Architecture:              |        Blocked By:
  Unknown/Multiple                   |   Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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 The User's Guide .xml files use a fairly random-looking mix of tabs and
 spaces for indentation. Let's get rid of the tabs and then enforce their
 absence with git hooks.

 Why do this? See #10425; apparently tabs within programlisting elements
 are rendered as some number of spaces other than 8 in the PDF version
 (only!) I briefly tried to find other instances of the same issue, but
 there are thousands of tab characters in the User's Guide and I'm too lazy
 to try to find only the ones within programlisting elements.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10475>
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