feat: hyperlink trailing pr mention in commit summary

src/main/java/io/papermc/fill/discord/DiscordNotifier.java

@@ -43,6 +43,7 @@
 import io.papermc.fill.util.BuildPublishListener;
 import io.papermc.fill.util.discord.Components;
 import io.papermc.fill.util.discord.DiscordNotificationChannel;
+import io.papermc.fill.util.discord.PrToMdHyperLinkUtil;
 import io.papermc.fill.util.git.GitRepository;
 import java.net.URI;
 import java.util.List;
@@ -147,7 +148,7 @@ private Container createContent(final ProjectEntity project, final Version versi
               repository.name(),
               commit.sha()
             ),
-            commit.summary()
+            PrToMdHyperLinkUtil.hyperlinkTrailingPrMention(commit.summary(), repository.owner(), repository.name())
           )).collect(Collectors.joining("\n"))
       ));
     }, switch (build.channel()) {

src/main/java/io/papermc/fill/util/discord/PrToMdHyperLinkUtil.java

@@ -0,0 +1,32 @@
+package io.papermc.fill.util.discord;
+
+import java.util.Objects;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import org.jspecify.annotations.NullMarked;
+
+@NullMarked
+public class PrToMdHyperLinkUtil {
+  private static final Pattern TRAILING_PR = Pattern.compile(" \\(#(\\d+)\\)\\z");
+
+  private PrToMdHyperLinkUtil() {
+  }
+
+
+  public  static String hyperlinkTrailingPrMention(final String commitSummary, final String repoOwner, final String repoName) {
+    Objects.requireNonNull(commitSummary);
+    Objects.requireNonNull(repoOwner);
+    Objects.requireNonNull(repoName);
+
+    if (commitSummary.isEmpty()) return commitSummary;
+
+    final Matcher matcher = TRAILING_PR.matcher(commitSummary);
+    if (!matcher.find()) return commitSummary;
+
+    final String prNumber = matcher.group(1);
+
+    return matcher.replaceFirst(
+      String.format(" ([#%s](https://github.com/%s/%s/pull/%s))",
+        prNumber, repoOwner, repoName, prNumber));
+  }
+}

src/test/java/io/papermc/fill/model/util/discord/PrToMdHyperLinkUtilTest.java

@@ -0,0 +1,54 @@
+package io.papermc.fill.model.util.discord;
+
+import io.papermc.fill.util.discord.PrToMdHyperLinkUtil;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+class PrToMdHyperLinkUtilTest {
+  @ParameterizedTest
+  @ValueSource(strings = {
+    "no mention",
+    "(#36) not trailing",
+    "missing space(#72)",
+    "not in brackets #72",
+    ""
+  })
+  void returnsUnchangedForInvalidCases(String commitSummary) {
+    String actual = PrToMdHyperLinkUtil.hyperlinkTrailingPrMention(commitSummary, "myOrg", "myRepo");
+    assertEquals(commitSummary, actual);
+  }
+
+  @ParameterizedTest
+  @CsvSource({
+    "Rework broken xyz (#123), myOrg, myRepo, Rework broken xyz ([#123](https://github.com/myOrg/myRepo/pull/123))",
+    "Don't run player loot table for spectators (#11801), PaperMC, Paper, Don't run player loot table for spectators ([#11801](https://github.com/PaperMC/Paper/pull/11801))",
+    "feat: add new xyz API   (#12), myOrg, myRepo, feat: add new xyz API   ([#12](https://github.com/myOrg/myRepo/pull/12))",
+    "Fix (#1234) via xyz (#4125), myOrg, myRepo, Fix (#1234) via xyz ([#4125](https://github.com/myOrg/myRepo/pull/4125))"
+  })
+  void replacesTrailingPrMentionWithMarkdownLink(String commitSummary, String repoOwner, String repoName, String expected) {
+    String actual = PrToMdHyperLinkUtil.hyperlinkTrailingPrMention(commitSummary, repoOwner, repoName);
+    assertEquals(expected, actual);
+  }
+
+  @ParameterizedTest
+  @CsvSource({
+    "commitSummary, null, myOrg, myRepo",
+    "repoOwner, working summary (#1), null, myRepo",
+    "repoName, working summary (#1), myOrg, null"
+  })
+  @SuppressWarnings("DataFlowIssue")
+  void nullParameterThrowsNPE(String parameter, String commitSummary, String repoOwner, String repoName) {
+    assertThrows(NullPointerException.class, () ->
+        PrToMdHyperLinkUtil.hyperlinkTrailingPrMention(
+          "null".equals(commitSummary) ? null : commitSummary,
+          "null".equals(repoOwner) ? null : repoOwner,
+          "null".equals(repoName) ? null : repoName
+        ),
+      () -> "Expected NullPointerException for parameter " + parameter
+    );
+  }
+}