fix: resolve GHCommitPointer commit when the head repository is deleted

src/main/java/org/kohsuke/github/GHCommitPointer.java

@@ -35,9 +35,12 @@
  */
 public class GHCommitPointer {
 
-    private String ref, sha, label;
+    /** The pull request this pointer belongs to, used when {@link #repo} is unavailable. */
+    private transient GHPullRequest pullRequest;
 
+    private String ref, sha, label;
     private GHRepository repo;
+
     private GHUser user;
     /**
      * Create default GHCommitPointer instance
@@ -48,12 +51,23 @@ public GHCommitPointer() {
     /**
      * Obtains the commit that this pointer is referring to.
      *
+     * If the repository is unavailable (for example, the head repository of a pull request opened from a fork that has
+     * since been deleted), the commit is looked up in the repository of the pull request instead. GitHub keeps pull
+     * request commits in the base repository, so they remain reachable there.
+     *
      * @return the commit
      * @throws IOException
      *             the io exception
      */
     public GHCommit getCommit() throws IOException {
-        return getRepository().getCommit(getSha());
+        GHRepository repository = getRepository();
+        if (repository == null && pullRequest != null) {
+            repository = pullRequest.getRepository();
+        }
+        if (repository == null) {
+            throw new IOException("Repository information is unavailable for commit " + getSha());
+        }
+        return repository.getCommit(getSha());
     }
 
     /**
@@ -77,7 +91,10 @@ public String getRef() {
     /**
      * The repository that contains the commit.
      *
-     * @return the repository
+     * This value is {@code null} when GitHub does not report a repository, for example when the head repository of a
+     * pull request has been deleted. {@link #getCommit()} still works in that case.
+     *
+     * @return the repository, or {@code null} when it is unavailable
      */
     @SuppressFBWarnings(value = { "EI_EXPOSE_REP" }, justification = "Expected behavior")
     public GHRepository getRepository() {
@@ -105,4 +122,15 @@ public GHUser getUser() {
         return user;
     }
 
+    /**
+     * Binds this pointer to the pull request it belongs to.
+     *
+     * @param pullRequest
+     *            the pull request
+     * @return this pointer
+     */
+    GHCommitPointer wrapUp(GHPullRequest pullRequest) {
+        this.pullRequest = pullRequest;
+        return this;
+    }
 }

src/main/java/org/kohsuke/github/GHPullRequest.java

@@ -272,7 +272,7 @@ public AutoMerge getAutoMerge() {
      * @return the base
      */
     public GHCommitPointer getBase() {
-        return base;
+        return base == null ? null : base.wrapUp(this);
     }
 
     /**
@@ -340,7 +340,7 @@ public URL getDiffUrl() {
      * @return the head
      */
     public GHCommitPointer getHead() {
-        return head;
+        return head == null ? null : head.wrapUp(this);
     }
 
     /**

src/test/java/org/kohsuke/github/GHCommitPointerTest.java

@@ -0,0 +1,89 @@
+package org.kohsuke.github;
+
+import com.github.tomakehurst.wiremock.client.WireMock;
+import org.junit.Test;
+
+import java.io.IOException;
+
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.notNullValue;
+import static org.hamcrest.Matchers.nullValue;
+import static org.junit.Assert.assertThrows;
+
+// TODO: Auto-generated Javadoc
+/**
+ * The Class GHCommitPointerTest.
+ */
+public class GHCommitPointerTest extends AbstractGitHubWireMockTest {
+
+    /**
+     * Create default GHCommitPointerTest instance
+     */
+    public GHCommitPointerTest() {
+    }
+
+    /**
+     * The head of checkstyle/checkstyle#1 comes from a fork that no longer exists, so GitHub reports its repository as
+     * {@code null}. The head commit is still reachable through the base repository.
+     *
+     * @throws Exception
+     *             the exception
+     */
+    @Test
+    public void getCommitFromDeletedHeadRepository() throws Exception {
+        GHPullRequest pullRequest = gitHub.getRepository("checkstyle/checkstyle").getPullRequest(1);
+        GHCommitPointer head = pullRequest.getHead();
+        assertThat(head.getRepository(), nullValue());
+        assertThat(head.getSha(), equalTo("4889a777da54c6848b92da273a28223cfaf8dfe9"));
+
+        GHCommit commit = head.getCommit();
+        assertThat(commit, notNullValue());
+        assertThat(commit.getSHA1(), equalTo("4889a777da54c6848b92da273a28223cfaf8dfe9"));
+        assertThat(commit.getOwner().getFullName(), equalTo("checkstyle/checkstyle"));
+
+        // Base still has its repository, so getCommit() must use that repository instead of the pull-request fallback.
+        // The recorded commit body is only for the head SHA; serve the same shape for the base SHA.
+        GHCommitPointer base = pullRequest.getBase();
+        assertThat(base, notNullValue());
+        assertThat(base.getRepository(), notNullValue());
+        assertThat(base.getRepository().getFullName(), equalTo("checkstyle/checkstyle"));
+        String baseSha = base.getSha();
+        mockGitHub.apiServer()
+                .stubFor(WireMock.get(WireMock.urlPathEqualTo("/repos/checkstyle/checkstyle/commits/" + baseSha))
+                        .withHeader("Accept", WireMock.equalTo("application/vnd.github+json"))
+                        .willReturn(WireMock.aResponse()
+                                .withStatus(200)
+                                .withHeader("Content-Type", "application/json; charset=utf-8")
+                                .withBody("{\"sha\":\"" + baseSha + "\"}")));
+
+        GHCommit baseCommit = base.getCommit();
+        assertThat(baseCommit, notNullValue());
+        assertThat(baseCommit.getSHA1(), equalTo(baseSha));
+        assertThat(baseCommit.getOwner().getFullName(), equalTo("checkstyle/checkstyle"));
+    }
+
+    /**
+     * A pointer that has neither a repository nor a pull request cannot resolve its commit.
+     *
+     * @throws Exception
+     *             the exception
+     */
+    @Test
+    public void getCommitWithoutRepositoryOrPullRequest() throws Exception {
+        snapshotNotAllowed();
+        GHCommitPointer pointer = new GHCommitPointer();
+        IOException failure = assertThrows(IOException.class, pointer::getCommit);
+        assertThat(failure.getMessage(), equalTo("Repository information is unavailable for commit null"));
+    }
+
+    /**
+     * {@link GHPullRequest#getHead()} and {@link GHPullRequest#getBase()} return null when the pointer was not set.
+     */
+    @Test
+    public void getHeadAndBaseWhenUnset() {
+        snapshotNotAllowed();
+        GHPullRequest pullRequest = new GHPullRequest();
+        assertThat(pullRequest.getHead(), nullValue());
+        assertThat(pullRequest.getBase(), nullValue());
+    }
+}

src/test/resources/org/kohsuke/github/GHCommitPointerTest/wiremock/getCommitFromDeletedHeadRepository/__files/1-user.json

@@ -0,0 +1,36 @@
+{
+  "login": "mvanhorn",
+  "id": 455140,
+  "node_id": "MDQ6VXNlcjQ1NTE0MA==",
+  "avatar_url": "https://avatars.githubusercontent.com/u/455140?v=4",
+  "gravatar_id": "",
+  "url": "https://api.github.com/users/mvanhorn",
+  "html_url": "https://github.com/mvanhorn",
+  "followers_url": "https://api.github.com/users/mvanhorn/followers",
+  "following_url": "https://api.github.com/users/mvanhorn/following{/other_user}",
+  "gists_url": "https://api.github.com/users/mvanhorn/gists{/gist_id}",
+  "starred_url": "https://api.github.com/users/mvanhorn/starred{/owner}{/repo}",
+  "subscriptions_url": "https://api.github.com/users/mvanhorn/subscriptions",
+  "organizations_url": "https://api.github.com/users/mvanhorn/orgs",
+  "repos_url": "https://api.github.com/users/mvanhorn/repos",
+  "events_url": "https://api.github.com/users/mvanhorn/events{/privacy}",
+  "received_events_url": "https://api.github.com/users/mvanhorn/received_events",
+  "type": "User",
+  "user_view_type": "public",
+  "site_admin": false,
+  "name": "Matt Van Horn",
+  "company": null,
+  "blog": "",
+  "location": null,
+  "email": null,
+  "hireable": null,
+  "bio": "Co-founded June (\"self-driving oven\" acquired by @webergrills) & the co that became @Lyft. Building again, more soon. OS: @slashlast30days 47k★ @ppressdev 5.4k★",
+  "twitter_username": "mvanhorn",
+  "notification_email": null,
+  "public_repos": 2860,
+  "public_gists": 1,
+  "followers": 5590,
+  "following": 7,
+  "created_at": "2010-10-26T19:09:59Z",
+  "updated_at": "2026-10-22T06:09:50Z"
+}

src/test/resources/org/kohsuke/github/GHCommitPointerTest/wiremock/getCommitFromDeletedHeadRepository/__files/2-r_c_checkstyle.json

@@ -0,0 +1,148 @@
+{
+  "id": 12499251,
+  "node_id": "MDEwOlJlcG9zaXRvcnkxMjQ5OTI1MQ==",
+  "name": "checkstyle",
+  "full_name": "checkstyle/checkstyle",
+  "private": false,
+  "owner": {
+    "login": "checkstyle",
+    "id": 5179750,
+    "node_id": "MDEyOk9yZ2FuaXphdGlvbjUxNzk3NTA=",
+    "avatar_url": "https://avatars.githubusercontent.com/u/5179750?v=4",
+    "gravatar_id": "",
+    "url": "https://api.github.com/users/checkstyle",
+    "html_url": "https://github.com/checkstyle",
+    "followers_url": "https://api.github.com/users/checkstyle/followers",
+    "following_url": "https://api.github.com/users/checkstyle/following{/other_user}",
+    "gists_url": "https://api.github.com/users/checkstyle/gists{/gist_id}",
+    "starred_url": "https://api.github.com/users/checkstyle/starred{/owner}{/repo}",
+    "subscriptions_url": "https://api.github.com/users/checkstyle/subscriptions",
+    "organizations_url": "https://api.github.com/users/checkstyle/orgs",
+    "repos_url": "https://api.github.com/users/checkstyle/repos",
+    "events_url": "https://api.github.com/users/checkstyle/events{/privacy}",
+    "received_events_url": "https://api.github.com/users/checkstyle/received_events",
+    "type": "Organization",
+    "user_view_type": "public",
+    "site_admin": false
+  },
+  "html_url": "https://github.com/checkstyle/checkstyle",
+  "description": "Checkstyle is a development tool to help programmers write Java code that adheres to a coding standard. By default it supports the Google Java Style Guide and Sun Code Conventions, but is highly configurable. It can be invoked with an ANT task and a command line program.",
+  "fork": false,
+  "url": "https://api.github.com/repos/checkstyle/checkstyle",
+  "forks_url": "https://api.github.com/repos/checkstyle/checkstyle/forks",
+  "keys_url": "https://api.github.com/repos/checkstyle/checkstyle/keys{/key_id}",
+  "collaborators_url": "https://api.github.com/repos/checkstyle/checkstyle/collaborators{/collaborator}",
+  "teams_url": "https://api.github.com/repos/checkstyle/checkstyle/teams",
+  "hooks_url": "https://api.github.com/repos/checkstyle/checkstyle/hooks",
+  "issue_events_url": "https://api.github.com/repos/checkstyle/checkstyle/issues/events{/number}",
+  "events_url": "https://api.github.com/repos/checkstyle/checkstyle/events",
+  "assignees_url": "https://api.github.com/repos/checkstyle/checkstyle/assignees{/user}",
+  "branches_url": "https://api.github.com/repos/checkstyle/checkstyle/branches{/branch}",
+  "tags_url": "https://api.github.com/repos/checkstyle/checkstyle/tags",
+  "blobs_url": "https://api.github.com/repos/checkstyle/checkstyle/git/blobs{/sha}",
+  "git_tags_url": "https://api.github.com/repos/checkstyle/checkstyle/git/tags{/sha}",
+  "git_refs_url": "https://api.github.com/repos/checkstyle/checkstyle/git/refs{/sha}",
+  "trees_url": "https://api.github.com/repos/checkstyle/checkstyle/git/trees{/sha}",
+  "statuses_url": "https://api.github.com/repos/checkstyle/checkstyle/statuses/{sha}",
+  "languages_url": "https://api.github.com/repos/checkstyle/checkstyle/languages",
+  "stargazers_url": "https://api.github.com/repos/checkstyle/checkstyle/stargazers",
+  "contributors_url": "https://api.github.com/repos/checkstyle/checkstyle/contributors",
+  "subscribers_url": "https://api.github.com/repos/checkstyle/checkstyle/subscribers",
+  "subscription_url": "https://api.github.com/repos/checkstyle/checkstyle/subscription",
+  "commits_url": "https://api.github.com/repos/checkstyle/checkstyle/commits{/sha}",
+  "git_commits_url": "https://api.github.com/repos/checkstyle/checkstyle/git/commits{/sha}",
+  "comments_url": "https://api.github.com/repos/checkstyle/checkstyle/comments{/number}",
+  "issue_comment_url": "https://api.github.com/repos/checkstyle/checkstyle/issues/comments{/number}",
+  "contents_url": "https://api.github.com/repos/checkstyle/checkstyle/contents/{+path}",
+  "compare_url": "https://api.github.com/repos/checkstyle/checkstyle/compare/{base}...{head}",
+  "merges_url": "https://api.github.com/repos/checkstyle/checkstyle/merges",
+  "archive_url": "https://api.github.com/repos/checkstyle/checkstyle/{archive_format}{/ref}",
+  "downloads_url": "https://api.github.com/repos/checkstyle/checkstyle/downloads",
+  "issues_url": "https://api.github.com/repos/checkstyle/checkstyle/issues{/number}",
+  "pulls_url": "https://api.github.com/repos/checkstyle/checkstyle/pulls{/number}",
+  "milestones_url": "https://api.github.com/repos/checkstyle/checkstyle/milestones{/number}",
+  "notifications_url": "https://api.github.com/repos/checkstyle/checkstyle/notifications{?since,all,participating}",
+  "labels_url": "https://api.github.com/repos/checkstyle/checkstyle/labels{/name}",
+  "releases_url": "https://api.github.com/repos/checkstyle/checkstyle/releases{/id}",
+  "deployments_url": "https://api.github.com/repos/checkstyle/checkstyle/deployments",
+  "created_at": "2013-08-31T02:05:05Z",
+  "updated_at": "2026-10-23T12:15:07Z",
+  "pushed_at": "2026-10-23T13:53:31Z",
+  "git_url": "git://github.com/checkstyle/checkstyle.git",
+  "ssh_url": "git@github.com:checkstyle/checkstyle.git",
+  "clone_url": "https://github.com/checkstyle/checkstyle.git",
+  "svn_url": "https://github.com/checkstyle/checkstyle",
+  "homepage": "https://checkstyle.org",
+  "size": 321106,
+  "stargazers_count": 9616,
+  "watchers_count": 9616,
+  "language": "Java",
+  "has_issues": true,
+  "has_projects": true,
+  "has_downloads": false,
+  "has_wiki": true,
+  "has_pages": false,
+  "has_discussions": true,
+  "forks_count": 4300,
+  "mirror_url": null,
+  "archived": false,
+  "disabled": false,
+  "open_issues_count": 821,
+  "license": {
+    "key": "lgpl-2.1",
+    "name": "GNU Lesser General Public License v2.1",
+    "spdx_id": "LGPL-2.1",
+    "url": "https://api.github.com/licenses/lgpl-2.1",
+    "node_id": "MDc6TGljZW5zZTEx"
+  },
+  "allow_forking": true,
+  "is_template": false,
+  "web_commit_signoff_required": false,
+  "has_pull_requests": true,
+  "pull_request_creation_policy": "all",
+  "topics": [
+    "code-quality",
+    "command-line-tool",
+    "hacktoberfest",
+    "java",
+    "static-analysis",
+    "static-code-analysis"
+  ],
+  "visibility": "public",
+  "forks": 4300,
+  "open_issues": 821,
+  "watchers": 9616,
+  "default_branch": "master",
+  "permissions": {
+    "admin": false,
+    "maintain": false,
+    "push": false,
+    "triage": false,
+    "pull": true
+  },
+  "temp_clone_token": "",
+  "custom_properties": {},
+  "organization": {
+    "login": "checkstyle",
+    "id": 5179750,
+    "node_id": "MDEyOk9yZ2FuaXphdGlvbjUxNzk3NTA=",
+    "avatar_url": "https://avatars.githubusercontent.com/u/5179750?v=4",
+    "gravatar_id": "",
+    "url": "https://api.github.com/users/checkstyle",
+    "html_url": "https://github.com/checkstyle",
+    "followers_url": "https://api.github.com/users/checkstyle/followers",
+    "following_url": "https://api.github.com/users/checkstyle/following{/other_user}",
+    "gists_url": "https://api.github.com/users/checkstyle/gists{/gist_id}",
+    "starred_url": "https://api.github.com/users/checkstyle/starred{/owner}{/repo}",
+    "subscriptions_url": "https://api.github.com/users/checkstyle/subscriptions",
+    "organizations_url": "https://api.github.com/users/checkstyle/orgs",
+    "repos_url": "https://api.github.com/users/checkstyle/repos",
+    "events_url": "https://api.github.com/users/checkstyle/events{/privacy}",
+    "received_events_url": "https://api.github.com/users/checkstyle/received_events",
+    "type": "Organization",
+    "user_view_type": "public",
+    "site_admin": false
+  },
+  "network_count": 4300,
+  "subscribers_count": 223
+}