Adding support for getting a PR's patch.

This also adds a new request method that accepts extra headers and doesn't try to parse JSON

src/main/java/com/spotify/github/v3/clients/GitHubClient.java

@@ -391,6 +391,21 @@ CompletableFuture<Response> request(final String path) {
     return call(request);
   }
 
+  /**
+   * Make an http GET request for the given path on the server
+   *
+   * @param path relative to the Github base url
+   * @param extraHeaders extra github headers to be added to the call
+   * @return a reader of response body
+   */
+  CompletableFuture<Response> request(final String path, final Map<String, String> extraHeaders) {
+    final Request.Builder builder = requestBuilder(path);
+    extraHeaders.forEach(builder::addHeader);
+    final Request request = builder.build();
+    log.debug("Making request to {}", request.url().toString());
+    return call(request);
+  }
+
   /**
    * Make an http GET request for the given path on the server
    *

src/main/java/com/spotify/github/v3/clients/PullRequestClient.java

@@ -25,18 +25,23 @@
 import static com.spotify.github.v3.clients.GitHubClient.LIST_PR_TYPE_REFERENCE;
 import static com.spotify.github.v3.clients.GitHubClient.LIST_REVIEW_REQUEST_TYPE_REFERENCE;
 import static com.spotify.github.v3.clients.GitHubClient.LIST_REVIEW_TYPE_REFERENCE;
+import static java.util.Objects.isNull;
 
 import com.google.common.base.Strings;
+import com.google.common.collect.ImmutableMap;
 import com.spotify.github.async.AsyncPage;
 import com.spotify.github.v3.prs.*;
 import com.spotify.github.v3.prs.requests.PullRequestCreate;
 import com.spotify.github.v3.prs.requests.PullRequestParameters;
 import com.spotify.github.v3.prs.requests.PullRequestUpdate;
 import com.spotify.github.v3.repos.CommitItem;
+import java.io.Reader;
 import java.lang.invoke.MethodHandles;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Map;
 import java.util.concurrent.CompletableFuture;
+import javax.ws.rs.core.HttpHeaders;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -227,6 +232,22 @@ public CompletableFuture<Void> merge(final int number, final MergeParameters pro
     return github.put(path, jsonPayload).thenAccept(IGNORE_RESPONSE_CONSUMER);
   }
 
+  public CompletableFuture<Reader> patch(final int number) {
+    final String path = String.format(PR_NUMBER_TEMPLATE, owner, repo, number);
+    final Map<String, String> extraHeaders = ImmutableMap.of(
+        HttpHeaders.ACCEPT, "application/vnd.github.patch"
+    );
+    log.debug("Fetching pull request patch from " + path);
+    return github.request(path, extraHeaders)
+        .thenApply(response -> {
+          final var body = response.body();
+          if (isNull(body)) {
+            return Reader.nullReader();
+          }
+          return body.charStream();
+        });
+  }
+
   private CompletableFuture<List<PullRequestItem>> list(final String parameterPath) {
     final String path = String.format(PR_TEMPLATE + parameterPath, owner, repo);
     log.debug("Fetching pull requests from " + path);

src/test/java/com/spotify/github/v3/clients/PullRequestClientTest.java

@@ -46,6 +46,7 @@
 import com.spotify.github.v3.prs.requests.PullRequestCreate;
 import com.spotify.github.v3.prs.requests.PullRequestUpdate;
 import java.io.IOException;
+import java.io.Reader;
 import java.net.URI;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutionException;
@@ -57,6 +58,7 @@
 import okhttp3.Request;
 import okhttp3.Response;
 import okhttp3.ResponseBody;
+import org.apache.commons.io.IOUtils;
 import org.junit.Before;
 import org.junit.Test;
 import org.mockito.ArgumentCaptor;
@@ -259,4 +261,37 @@ public void testRemoveRequestedReview_failure() throws Throwable {
       // expecting RequestNotOkException
     }
   }
+
+  @Test
+  public void testGetPatch() throws Throwable {
+    final Call call = mock(Call.class);
+    final ArgumentCaptor<Callback> capture = ArgumentCaptor.forClass(Callback.class);
+    doNothing().when(call).enqueue(capture.capture());
+
+    final Response response =
+        new Response.Builder()
+            .code(200)
+            .protocol(Protocol.HTTP_1_1)
+            .message("OK")
+            .body(
+                ResponseBody.create(
+                    MediaType.get("application/vnd.github.patch"),
+                    getFixture("patch.txt")))
+            .request(new Request.Builder().url("http://localhost/").build())
+            .build();
+
+    when(client.newCall(any())).thenReturn(call);
+
+    final PullRequestClient pullRequestClient =
+        PullRequestClient.create(github, "owner", "repo");
+
+    final CompletableFuture<Reader> result =
+        pullRequestClient.patch(1);
+
+    capture.getValue().onResponse(call, response);
+
+    Reader patchReader = result.get();
+
+    assertEquals(getFixture("patch.txt"), IOUtils.toString(patchReader));
+  }
 }

src/test/resources/com/spotify/github/v3/clients/patch.txt

@@ -0,0 +1,18 @@
+From 81c53612268423500bb086afbf7f6545a97ce181 Thu Jul 17 00:00:00 2000
+From: Spotify <office@spotify.com>
+Date: Thu, 17 Jul 2023 22:12:00 -0700
+Subject: [PATCH] Update filename
+
+---
+ filename | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/filename b/filename
+index 01a9f34..500bb03 100644
+--- a/nf
++++ b/nf
+@@ -1,3 +1,4 @@
+ asdf
++asdf
+--
+2.39.0