gitweb: Refactor syntax highlighting support

This refactoring (adding guess_file_syntax and run_highlighter
subroutines) is meant to make it easier in the future to add support
for other syntax highlighing solutions, or make it smarter by not
re-running `git cat-file` second time.

Instead of looping over list of regexps (keys of %highlight_type hash),
make use of the fact that choosing syntax is based either on full
basename (%highlight_basename), or on file extension (%highlight_ext).

Add some basic test of syntax highlighting (with 'highlight' as
prerequisite) to t/t9500-gitweb-standalone-no-errors.sh test.

While at it make git_blob Perl style prettier.

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Acked-by: Petr Baudis <pasky@suse.cz>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t9500-gitweb-standalone-no-errors.sh

@@ -647,4 +647,33 @@ test_expect_success \
 	 gitweb_run "p=.git;a=summary"'
 test_debug 'cat gitweb.log'
 
+# ----------------------------------------------------------------------
+# syntax highlighting
+
+cat >>gitweb_config.perl <<\EOF
+$feature{'highlight'}{'override'} = 1;
+EOF
+
+highlight --version >/dev/null 2>&1
+if [ $? -eq 127 ]; then
+	say "Skipping syntax highlighting test, because 'highlight' was not found"
+else
+	test_set_prereq HIGHLIGHT
+fi
+
+test_expect_success HIGHLIGHT \
+	'syntax highlighting (no highlight)' \
+	'git config gitweb.highlight yes &&
+	 gitweb_run "p=.git;a=blob;f=file"'
+test_debug 'cat gitweb.log'
+
+test_expect_success HIGHLIGHT \
+	'syntax highlighting (highlighted)' \
+	'git config gitweb.highlight yes &&
+	 echo "#!/usr/bin/sh" > test.sh &&
+	 git add test.sh &&
+	 git commit -m "Add test.sh" &&
+	 gitweb_run "p=.git;a=blob;f=test.sh"'
+test_debug 'cat gitweb.log'
+
 test_done