Generate diff link for first release

And include the "v" for the version tag in the diff.

.ci/mknotes

@@ -75,13 +75,23 @@ sub run {
                 $in_item = $self->print_line($out, $line, $in_item)
                     unless $line =~ $link_regex;
 			}
+            # Reach the end of the file; must be the first release. Diff the
+            # initial commit.
+            return $self->finish_list($out, $self->initial_commit);
         }
     }
 
     # All done!
     die "Version $self->{version} not found in $self->{file}\n" unless $found;
 }
 
+# Called when no previous releases found. Return the initial commit in
+# brackets to be parsed by finish_list().
+sub initial_commit {
+    my $sha = qx(git rev-list --max-parents=0 HEAD);
+    return "["  . substr($sha, 0, 7) . "]";
+}
+
 # Called when the next version header is found in line.
 sub finish_list {
     my ($self, $out, $line) = @_;
@@ -92,7 +102,7 @@ sub finish_list {
 
 	# Emit a footer line with a link to the diff for this version.
     print {$out} sprintf(
-		"---\n\n🆚 For more detail compare [changes since %s](%s/compare/%s...%s).\n",
+		"---\n\n🆚 For more detail compare [changes since %s](%s/compare/%s...v%s).\n",
 		$prev, $self->{repo}, $prev, $self->{version},
 	);
 

CHANGELOG.md

@@ -46,7 +46,7 @@ The theme of this release is *learning Rust and pgrx.*
 *   Performance [benchmark script]
 *   Multi-schema [composition example]
 
-  [v0.1.0]: https://github.com/tembo-io/pg-jsonschema-boon/compare/34d5d49...HEAD
+  [v0.1.0]: https://github.com/tembo-io/pg-jsonschema-boon/compare/34d5d49...v0.1.0
   [boon]: https://github.com/santhosh-tekuri/boon
   [README]: https://github.com/tembo-io/pg-jsonschema-boon/blob/v0.1.0/README.md
   [PGXN]: https://pgxn.org/dist/jsonschema/