Documentation: modernize cat-texi.perl

Good style for Perl includes using the strict and warnings pragmas, and
preferring lexical file handles over bareword file handles.  Using
lexical file handles necessitates being explicit when $_ is printed, so
that Perl does not get confused and instead print the glob ref.

The benefit of this modernization is that a formerly obscured bug is now
visible, which will be fixed in a followup patch.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/cat-texi.perl

@@ -1,9 +1,12 @@
 #!/usr/bin/perl -w
 
+use strict;
+use warnings;
+
 my @menu = ();
 my $output = $ARGV[0];
 
-open TMP, '>', "$output.tmp";
+open my $tmp, '>', "$output.tmp";
 
 while (<STDIN>) {
 	next if (/^\\input texinfo/../\@node Top/);
@@ -13,9 +16,9 @@ while (<STDIN>) {
 	}
 	s/\(\@pxref\{\[(URLS|REMOTES)\]}\)//;
 	s/\@anchor\{[^{}]*\}//g;
-	print TMP;
+	print $tmp $_;
 }
-close TMP;
+close $tmp;
 
 printf '\input texinfo
 @setfilename gitman.info
@@ -34,10 +37,10 @@ for (@menu) {
 	print "* ${_}::\n";
 }
 print "\@end menu\n";
-open TMP, '<', "$output.tmp";
+open $tmp, '<', "$output.tmp";
-while (<TMP>) {
+while (<$tmp>) {
 	print;
 }
-close TMP;
+close $tmp;
 print "\@bye\n";
 unlink "$output.tmp";