pr: add /tag commit command

Reviewed-by: rwestberg

bots/pr/src/main/java/org/openjdk/skara/bots/pr/CommitCommandWorkItem.java

@@ -46,7 +46,8 @@ public class CommitCommandWorkItem implements WorkItem {
 
     private static final Map<String, CommandHandler> commandHandlers = Map.ofEntries(
             Map.entry("help", new HelpCommand()),
-            Map.entry("backport", new BackportCommand())
+            Map.entry("backport", new BackportCommand()),
+            Map.entry("tag", new TagCommand())
     );
 
     static class HelpCommand implements CommandHandler {

bots/pr/src/main/java/org/openjdk/skara/bots/pr/TagCommand.java

@@ -0,0 +1,120 @@
+/*
+ * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package org.openjdk.skara.bots.pr;
+
+import org.openjdk.skara.forge.HostedCommit;
+import org.openjdk.skara.forge.PullRequest;
+import org.openjdk.skara.issuetracker.Comment;
+import org.openjdk.skara.vcs.*;
+import org.openjdk.skara.vcs.openjdk.CommitMessageParsers;
+import org.openjdk.skara.jcheck.JCheckConfiguration;
+
+import java.io.PrintWriter;
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.time.format.DateTimeFormatter;
+
+public class TagCommand implements CommandHandler {
+    private void showHelp(PrintWriter reply) {
+        reply.println("Usage: `/tag <name>`");
+    }
+
+    @Override
+    public String description() {
+        return "Create a tag for the given commit";
+    }
+
+    @Override
+    public boolean allowedInCommit() {
+        return true;
+    }
+
+    @Override
+    public boolean allowedInPullRequest() {
+        return false;
+    }
+
+    @Override
+    public void handle(PullRequestBot bot, HostedCommit commit, CensusInstance censusInstance, Path scratchPath, CommandInvocation command, List<Comment> allComments, PrintWriter reply) {
+        try {
+            var username = command.user().username();
+            if (censusInstance.contributor(command.user()).isEmpty()) {
+                reply.println("@" + username + " only OpenJDK [contributors](https://openjdk.java.net/bylaws#contributor) can use the `/tag` command.");
+                return;
+            }
+            if (!bot.integrators().contains(username)) {
+                reply.println("@" + username + " only integrators for this repository are allowed to use the `/tag` command.");
+                return;
+            }
+
+            var args = command.args();
+            if (args.isBlank()) {
+                showHelp(reply);
+                return;
+            }
+
+            var parts = args.split(" ");
+            if (parts.length > 1) {
+                showHelp(reply);
+                return;
+            }
+            var tagName = parts[0];
+
+            var localRepoDir = scratchPath.resolve("tag-command")
+                                          .resolve(bot.repo().name());
+            var localRepo = bot.hostedRepositoryPool()
+                               .orElseThrow(() -> new IllegalStateException("Missing repository pool for PR bot"))
+                               .materialize(bot.repo(), localRepoDir);
+
+            var existingTagNames = localRepo.tags().stream().map(Tag::name).collect(Collectors.toSet());
+            if (existingTagNames.contains(tagName)) {
+                var hash = localRepo.resolve(tagName).orElseThrow(() ->
+                        new IllegalStateException("Cannot resolve tag with name " + tagName + " in repo " + bot.repo().name()));
+                var hashUrl = bot.repo().webUrl(hash);
+                reply.println("@" + username + " a tag with name `" + tagName + "` already exists that refers to commit [" + hash.abbreviate() + "](" + hashUrl + "].");
+                return;
+            }
+
+            var jcheckConf = JCheckConfiguration.from(localRepo, commit.hash());
+            var tagPattern = jcheckConf.isPresent() ? jcheckConf.get().repository().tags() : null;
+            if (tagPattern != null && !tagName.matches(tagPattern)) {
+                reply.println("@" + username + " the given tag name `" + tagName + "` is not of the form `" + tagPattern + "`.");
+                return;
+            }
+
+            var domain = censusInstance.configuration().census().domain();
+            var contributor = censusInstance.contributor(command.user()).orElseThrow();
+            var email = contributor.username() + "@" + domain;
+            var message = "Added tag " + tagName + " for changeset " + commit.hash().abbreviate();
+            var tag = localRepo.tag(commit.hash(), tagName, message, contributor.username(), email);
+            localRepo.push(tag, bot.repo().url(), false);
+            reply.println("@" + username + " the tag [" + tag.name() + "](" + bot.repo().webUrl(tag) + ") was successfully created.");
+        } catch (IOException e) {
+            throw new UncheckedIOException(e);
+        }
+    }
+}