doc: avoid needless rebuilds of NEWS

Repeatedly rebuilding `NEWS' because the mtime of `NEWS'
is synched to the latest release .eml is a bit annoying,
but necessary to save bandwidth for the website.

So we'll also update the mtime of the source .eml file when
reading them.  It's kinda gross to be setting mtimes of source
.eml files in Documentation/RelNotes/, but I can't think of
anything better at the moment...

1 files changed, 12 insertions, 4 deletions

diff --git a/Documentation/mknews.perl b/Documentation/mknews.perl
index 3efabdb5..71b1a996 100755
--- a/Documentation/mknews.perl
+++ b/Documentation/mknews.perl
@@ -21,8 +21,8 @@ my $atom_url = 'https://public-inbox.org/NEWS.atom';
 my $addr = 'meta@public-inbox.org';
 
 my $latest = shift(@releases) or die 'no releases?';
-my $mime_latest = release2mime($latest);
-my $mtime = msg_datestamp($mime_latest->header_obj);
+my $mtime;
+my $mime_latest = release2mime($latest, \$mtime);
 my $tmp = "$dst+";
 my $out;
 if ($dst eq 'NEWS') {
@@ -73,9 +73,17 @@ rename($tmp, $dst) or die;
 exit 0;
 
 sub release2mime {
-        my $f = "$dir/$_[0].eml";
+        my ($release, $mtime_ref) = @_;
+        my $f = "$dir/$release.eml";
         open(my $fh, '<', $f) or die "open($f): $!";
-        PublicInbox::MIME->new(do { local $/; <$fh> });
+        my $mime = PublicInbox::MIME->new(do { local $/; <$fh> });
+        # Documentation/include.mk relies on mtimes of each .eml file
+        # to trigger rebuild, so make sure we sync the mtime to the Date:
+        # header in the .eml
+        my $mtime = msg_datestamp($mime->header_obj);
+        utime($mtime, $mtime, $fh) or warn "futimes $f: $!";
+        $$mtime_ref = $mtime if $mtime_ref;
+        $mime;
 }
 
 sub mime2txt {