patchDocumentation/build-docdep.perl: generate sorted output

To make sure that our manpages are rebuilt when any of the included source files change and only the affected manpages are rebuilt, 'build-docdep.perl' scans our documentation source files for include directives, and outputs 'make' dependencies to be included by 'Documentation/Makefile'. This script relies on Perl's hash data structures, and generates its output while iterating over them, and since hashes in Perl are very much unordered, the output varies greatly from run to run, both the order of targets and the order of dependencies of each target.

This lack of ordering doesn't matter for 'make', because it cares neither about the order of targets in a Makefile nor about the order of a target's dependencies. However, it does matter to developers looking into build issues potentially involving these generated dependencies, as it's rather hard to tell whether there are any relevant (i.e. not order-only) changes among the dependencies compared to the previous run.

So let's make 'build-docdep.perl's output stable and ordered by sorting the keys of the hashes before iterating over them.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
---
 Documentation/build-docdep.perl | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

On Fri, Oct 21 2022, SZEDER Gábor wrote:

This looks good to me, FWIW I ran this ad-hoc test and it's the same,
i.e. we end up with the same order as the initial glob order on the FS:
	
	diff --git a/Documentation/build-docdep.perl b/Documentation/build-docdep.perl
	index ba4205e0302..6f6e6c62eb8 100755
	--- a/Documentation/build-docdep.perl
	+++ b/Documentation/build-docdep.perl
	@@ -1,9 +1,13 @@
	 #!/usr/bin/perl
	+use strict;
	+use warnings;
	 
	 my %include = ();
	 my %included = ();
	 
	-for my $text (<*.txt>) {
	+my @txt = <*.txt>;
	+
	+for my $text (@txt) {
	     open I, '<', $text || die "cannot read: $text";
	     while (<I>) {
	 	if (/^include::/) {
	@@ -38,9 +42,11 @@
	     }
	 }
	 
	-while (my ($text, $included) = each %include) {
	+
	+for my $text (grep { exists $include{$_} } @txt) {
	+    my $included = $include{$text};
	     if (! exists $included{$text} &&
	 	(my $base = $text) =~ s/\.txt$//) {
	-	print "$base.html $base.xml : ", join(" ", keys %$included), "\n";
	+	print "$base.html $base.xml : ", join(" ", sort keys %$included), "\n";
	     }
	 }
	

SZEDER Gábor <szeder.dev@gmail.com> writes:

Makes sense.  Will queue.