Fix #11 by asserting the git result that we expect.

CHANGELOG.md

@@ -6,7 +6,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 ### Fixed
-- Bug in `PoolString.concat(String)`.
+- Better error message for cases where the `spotlessChangelog` block is too low. ([#6](https://github.com/diffplug/spotless-changelog/issues/6))
+- Bug in `PoolString.concat(String)` ([1f6da65](https://github.com/diffplug/spotless-changelog/commit/1f6da65b51c5ee7af847dc0e427fe685fbd3d43c)).
+- No longer accepts git failures silently (they were always printed, but did not properly kill the build). ([#11](https://github.com/diffplug/spotless-changelog/issues/11))
 
 ## [1.1.0] - 2020-01-13
 ### Added

spotless-changelog-lib/src/main/java/com/diffplug/spotless/changelog/GitActions.java

@@ -22,19 +22,22 @@
 import java.util.Arrays;
 import java.util.List;
 import java.util.Objects;
+import java.util.Optional;
 import java.util.function.Consumer;
 import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.api.PushCommand;
 import org.eclipse.jgit.api.errors.GitAPIException;
 import org.eclipse.jgit.lib.ConfigConstants;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.Ref;
+import org.eclipse.jgit.lib.RefUpdate;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.storage.file.FileRepositoryBuilder;
 import org.eclipse.jgit.transport.CredentialsProvider;
 import org.eclipse.jgit.transport.PushResult;
 import org.eclipse.jgit.transport.RefSpec;
 import org.eclipse.jgit.transport.RemoteRefUpdate;
+import org.eclipse.jgit.transport.TrackingRefUpdate;
 import org.eclipse.jgit.transport.UsernamePasswordCredentialsProvider;
 
 /** API for doing the commit, tag, and push operations.  See {@link GitCfg#withChangelog(File, ChangelogAndNext)}. */
@@ -66,7 +69,7 @@ public void checkCanPush() throws GitAPIException, IOException {
 			if (!ref.getObjectId().equals(remoteRef.getObjectId())) {
 				throw new IllegalStateException("Local branch " + cfg.branch + " is out of sync with " + cfg.remote + ", so we can't safely push it automatically.");
 			}
-			push(cfg.branch);
+			push(cfg.branch, RefUpdate.Result.NO_CHANGE);
 		} catch (GitAPIException e) {
 			throw new IllegalArgumentException("You can set user/pass with any of these environment variables: " + envVars(), e);
 		}
@@ -95,8 +98,8 @@ public void addAndCommit() throws GitAPIException {
 	/** Tags and pushes the tag and the branch. */
 	public void tagBranchPush() throws GitAPIException {
 		Ref tagRef = git.tag().setName(tagName()).setAnnotated(false).call();
-		push(tagRef);
-		push(cfg.branch);
+		push(tagRef, RefUpdate.Result.NEW);
+		push(cfg.branch, RefUpdate.Result.FAST_FORWARD);
 	}
 
 	private String tagName() {
@@ -108,15 +111,15 @@ public void close() {
 		repository.close();
 	}
 
-	private void push(String branch) throws GitAPIException {
-		push(cmd -> cmd.add(branch));
+	private void push(String branch, RefUpdate.Result expected) throws GitAPIException {
+		push(cmd -> cmd.add(branch), expected);
 	}
 
-	private void push(Ref ref) throws GitAPIException {
-		push(cmd -> cmd.add(ref));
+	private void push(Ref ref, RefUpdate.Result expected) throws GitAPIException {
+		push(cmd -> cmd.add(ref), expected);
 	}
 
-	private void push(Consumer<PushCommand> cmd) throws GitAPIException {
+	private void push(Consumer<PushCommand> cmd, RefUpdate.Result expected) throws GitAPIException {
 		PushCommand push = git.push().setCredentialsProvider(creds()).setRemote(cfg.remote);
 		cmd.accept(push);
 
@@ -132,8 +135,14 @@ private void push(Consumer<PushCommand> cmd) throws GitAPIException {
 				+ "..."
 				+ (update.getNewObjectId() != null ? update.getNewObjectId().name() : "(null)")
 				+ (update.isFastForward() ? " fastForward" : "")
-				+ (update.getMessage() != null ? " " + update.getMessage() : ""));
-
+				+ (update.getMessage() != null ? update.getMessage() : ""));
+		Optional<RefUpdate.Result> failure = result.getTrackingRefUpdates().stream()
+				.map(TrackingRefUpdate::getResult)
+				.filter(r -> !expected.equals(r))
+				.findAny();
+		if (failure.isPresent()) {
+			throw new IllegalStateException("Error!  Expected " + expected + ", got " + failure.get());
+		}
 	}
 
 	// similar to https://github.com/ajoberstar/grgit/blob/5766317fbe67ec39faa4632e2b80c2b056f5c124/grgit-core/src/main/groovy/org/ajoberstar/grgit/auth/AuthConfig.groovy