Adjust long-description trimming to prefer trimming tag listing

Instead of cutting off the end of the image documentation, this change makes the code prefer to trim the entire "Supported tags" list, which for all our images which currently go over the limit brings them down enough to be within.  The note about where to get the full `README.md` file (with the "Supported tags" list intact) still stands, although could maybe do with some better styling and/or wording to make it more obvious (TBD).

I also verified that this change does the right thing in the fallback case by making the `postgres` image description intentionally extra long and verified that it simply trims the description content as before (since taking off the tags doesn't make the description short enough to be under the limit in that case).

push.pl

@@ -4,7 +4,7 @@ use warnings;
 use 5.010;
 use open ':encoding(utf8)';
 
-use File::Basename qw(fileparse);
+use File::Basename qw(basename fileparse);
 use File::Temp;
 use Getopt::Long;
 use Mojo::UserAgent;
@@ -14,7 +14,7 @@ use Term::UI;
 use Term::ReadLine;
 
 my $hubLengthLimit = 25_000;
-my $githubBase = 'https://github.com/docker-library/docs/tree/master';
+my $githubBase = 'https://github.com/docker-library/docs/tree/master'; # TODO point this at the correct "dist-xxx" branch based on "namespace"
 
 my $username;
 my $password;
@@ -80,18 +80,35 @@ sub prompt_for_edit {
 	if ($lengthLimit > 0 && length($proposedText) > $lengthLimit) {
 		# TODO https://github.com/docker/hub-beta-feedback/issues/238
 		my $fullUrl = "$githubBase/$proposedFile";
-		my $note = "**Note:** the description for this image is longer than the Hub length limit of $lengthLimit, so has been trimmed.  The full description can be found at [$fullUrl]($fullUrl).  See [docker/hub-beta-feedback#238](https://github.com/docker/hub-beta-feedback/issues/238) for more information.\n\n";
-		$proposedText = $note . substr $proposedText, 0, ($lengthLimit - length($note));
+		my $tagsNote = "**Note:** the description for this image is longer than the Hub length limit of $lengthLimit, so the \"Supported tags\" list has been trimmed to compensate.  The full list can be found at [$fullUrl]($fullUrl#supported-tags-and-respective-dockerfile-links).  See [docker/hub-beta-feedback#238](https://github.com/docker/hub-beta-feedback/issues/238) for more information.\n\n";
+		my $genericNote = "**Note:** the description for this image is longer than the Hub length limit of $lengthLimit, so has been trimmed.  The full description can be found at [$fullUrl]($fullUrl).  See [docker/hub-beta-feedback#238](https://github.com/docker/hub-beta-feedback/issues/238) for more information.\n\n";
+		
+		my $trimmedText = $proposedText;
+		
+		# if our text is too long for the Hub length limit, let's first try removing the "Supported tags" list and add $tagsNote and see if that's enough to let us put the full image documentation
+		$trimmedText =~ s%^(# Supported tags and respective `Dockerfile` links\n\n).*?\n(?=# |\[)%$1$tagsNote%ms;
+		# (we scrape until the next "h1" or a line starting with a link which is likely a build status badge for an architecture-namespace)
+		
+		if (length($trimmedText) > $lengthLimit) {
+			# ... if that doesn't do the trick, then do our older naïve description trimming
+			$trimmedText = $genericNote . substr $proposedText, 0, ($lengthLimit - length($genericNote));
+		}
+		
+		$proposedText = $trimmedText;
 	}
 	
 	return $currentText if $currentText eq $proposedText;
 	
 	my @proposedFileBits = fileparse($proposedFile, qr!\.[^.]*!);
-	my $file = File::Temp->new(SUFFIX => $proposedFileBits[2]);
+	my $file = File::Temp->new(SUFFIX => '-' . basename($proposedFileBits[1]) . '-current' . $proposedFileBits[2]);
 	my $filename = $file->filename;
 	spurt encode('UTF-8', $currentText . "\n"), $filename;
 	
-	system(qw(git --no-pager diff --no-index), $filename, $proposedFile);
+	my $tempProposedFile = File::Temp->new(SUFFIX => '-' . basename($proposedFileBits[1]) . '-proposed' . $proposedFileBits[2]);
+	my $tempProposedFilename = $tempProposedFile->filename;
+	spurt encode('UTF-8', $proposedText . "\n"), $tempProposedFilename;
+	
+	system(qw(git --no-pager diff --no-index), $filename, $tempProposedFilename);
 	
 	my $reply;
 	if ($batchmode) {
@@ -115,7 +132,7 @@ sub prompt_for_edit {
 	}
 	
 	if ($reply eq 'vimdiff') {
-		system('vimdiff', $filename, $proposedFile) == 0 or die "vimdiff on $filename and $proposedFile failed";
+		system('vimdiff', $tempProposedFilename, $filename) == 0 or die "vimdiff on $filename and $proposedFile failed";
 		return trim(decode('UTF-8', slurp($filename)));
 	}
 	

push.sh

@@ -6,4 +6,4 @@ cd "$(dirname "$(readlink -f "$BASH_SOURCE")")"
 #docker pull $(awk '$1 == "FROM" { print $2 }' Dockerfile)
 docker build -t docker-library-docs .
 test -t 1 && it='-it' || it='-i'
-docker run "$it" --rm -v "$(pwd)":/wtf -w /wtf -e TERM --entrypoint 'bash' docker-library-docs -c './push.pl "$@"' -- "$@"
+exec docker run "$it" --rm -v "$(pwd)":/wtf -w /wtf -e TERM --init --entrypoint ./push.pl docker-library-docs "$@"