gitweb: highlight: replace tabs with spaces

gitweb: highlight: replace tabs with spaces

Consider the following code fragment:

        /*
         * test
         */

vim ":set list" mode shows that the first character on each line is a
tab:

^I/*$
^I * test$
^I */$

By default, the "highlight" program will retain the tabs in the HTML
output:

$ highlight --fragment --syntax c test.c
        <span class="hl com">/*</span>
<span class="hl com">    * test</span>
<span class="hl com">    */</span>

vim list mode:

^I<span class="hl com">/*</span>$
<span class="hl com">^I * test</span>$
<span class="hl com">^I */</span>$

In gitweb, this winds up looking something like:

   1         /*
   2     * test
   3     */

I tried both Firefox and Opera and saw the same behavior.

The desired output is:

   1         /*
   2          * test
   3          */

This can be accomplished by specifying "--replace-tabs=8" on the
highlight command line.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Acked-by: John 'Warthog9' Hawley <warthog9@eaglescrag.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>