[PATCHv2 4/8] gitweb: Introduce esc_html_hl_regions

The esc_html_hl_regions() subroutine added in this commit is meant to highlight in a given string a list of regions (given as a list of [ beg, end ] pairs of positions in string), using HTML <span> element with given class.

It is to be used in next commit for highlighting matched part in project search.

Implementation and enhancement notes:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* Currently esc_html_hl_regions() subroutine doesn't accept any
  parameters, like esc_html() does.  We might want for example to
  pass  nbsp=>1  to it.

  It can easily be done with the following code:

    my %opts = grep { ref($_) ne "ARRAY" } @sel;
    @sel     = grep { ref($_) eq "ARRAY" } @sel;

  This allow adding parameters after or before regions, e.g.:

    esc_html_hl_regions("foo bar", "mark", [ 0, 3 ], -nbsp => 1);

* esc_html_hl_regions() escapes like esc_html(); if we wanted to
  highlight with esc_path(), we could pass subroutine reference
  to now named esc_gen_hl_regions().

    esc_html_hl_regions("foo bar", "mark", \&esc_path, [ 0, 3 ]);

  Note that this way we can handle -nbsp=>1 case automatically,
  e.g.

    esc_html_hl_regions("foo bar", "mark",
                        sub { esc_html(@_, -nbsp=>1) },
                        [ 0, 3 ]);

* Alternate solution for highlighting region of a string would be to
  use the idea that strings are to be HTML-escaped, and references to
  scalars are HTML (like in the idea for generic committags).

  This would require modifying gitweb code or esc_html to get list of
  fragments, e.g.:

    esc_html(\'<span class="mark">', 'foo', \'</span>', ' bar',
             { -nbsp => 1 });

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
---
This commit is here only for the notes in the commit message,
otherwise it could have been squashed with the next commit.

Note that we actually end up using first enhancement in notes section of the above commit message.

This patch is new; it was not present in v1

 gitweb/gitweb.perl |   27 +++++++++++++++++++++++++++
 1 files changed, 27 insertions(+), 0 deletions(-)