Add support for releaser.git.release-train-branch

This avoids guessing the branch

releaser-core/src/main/java/releaser/internal/ReleaserProperties.java

@@ -479,6 +479,7 @@ public class ReleaserProperties implements Serializable {
 		/**
 		 * Branch to check out for the release train project.
 		 */
+		// TODO: seems to only be for gh-docs? we guess when we could use this?
 		private String springProjectBranch;
 
 		/**
@@ -486,6 +487,11 @@ public class ReleaserProperties implements Serializable {
 		 */
 		private String testSamplesBranch;
 
+		/**
+		 * Branch to check out for the release train.
+		 */
+		private String releaseTrainBranch;
+
 		/**
 		 * Branch to check out for the release train docs.
 		 */
@@ -736,6 +742,14 @@ public class ReleaserProperties implements Serializable {
 			this.updateSpringProject = updateSpringProject;
 		}
 
+		public String getReleaseTrainBranch() {
+			return this.releaseTrainBranch;
+		}
+
+		public void setReleaseTrainBranch(String releaseTrainBranch) {
+			this.releaseTrainBranch = releaseTrainBranch;
+		}
+
 		public String getReleaseTrainDocsUrl() {
 			return this.releaseTrainDocsUrl;
 		}
@@ -813,6 +827,7 @@ public class ReleaserProperties implements Serializable {
 			return "Git{" + "releaseTrainBomUrl='" + this.releaseTrainBomUrl + '\''
 					+ ", documentationUrl='" + this.documentationUrl + '\''
 					+ ", documentationBranch='" + this.documentationBranch + '\''
+					+ ", releaseTrainBranch='" + this.releaseTrainBranch + '\''
 					+ ", releaseTrainWikiUrl='" + this.releaseTrainWikiUrl + '\''
 					+ ", updateDocumentationRepo=" + this.updateDocumentationRepo
 					+ ", springProjectUrl=" + this.springProjectUrl

releaser-core/src/main/java/releaser/internal/git/ProjectGitHandler.java

@@ -152,6 +152,18 @@ public class ProjectGitHandler implements Closeable {
 		if (log.isDebugEnabled()) {
 			log.debug("Successfully cloned the project to [{}]", clonedProject);
 		}
+		String releaseTrainBranch = this.properties.getGit().getReleaseTrainBranch();
+		if (!StringUtils.isEmpty(releaseTrainBranch)) {
+			if (log.isDebugEnabled()) {
+				log.debug("Checking out configured release train branch {}",
+						releaseTrainBranch);
+			}
+			if (gitRepo(clonedProject).hasBranch(releaseTrainBranch)) {
+				log.info("Branch [{}] exists. Will check it out", releaseTrainBranch);
+				checkout(clonedProject, releaseTrainBranch);
+			}
+			return clonedProject;
+		}
 		String version = this.properties.getFixedVersions().get(projectName);
 		if (StringUtils.isEmpty(version)) {
 			throw new IllegalStateException(

releaser-core/src/test/java/releaser/internal/buildsystem/ProjectVersionTests.java

@@ -152,7 +152,7 @@ public class ProjectVersionTests {
 		then(projectVersion("2.0.1.RC1").major()).isEqualTo("2");
 		then(projectVersion("Finchley.SR1").major()).isEqualTo("Finchley");
 		then(projectVersion("2020.0.0.M1").major()).isEqualTo("2020");
-		//then(projectVersion("2020.0.0").major()).isEqualTo("2020");
+		// then(projectVersion("2020.0.0").major()).isEqualTo("2020");
 	}
 
 	@Test
@@ -315,8 +315,8 @@ public class ProjectVersionTests {
 	public void should_return_true_when_checking_ga_version_against_ga() {
 		then(projectVersion("1.0.1.RELEASE").isReleaseOrServiceRelease()).isTrue();
 		then(projectVersion("1.0.1.SR1").isReleaseOrServiceRelease()).isTrue();
-		//then(projectVersion("1.0.0").isReleaseOrServiceRelease()).isTrue();
-		//then(projectVersion("1.0.1").isReleaseOrServiceRelease()).isTrue();
+		// then(projectVersion("1.0.0").isReleaseOrServiceRelease()).isTrue();
+		// then(projectVersion("1.0.1").isReleaseOrServiceRelease()).isTrue();
 	}
 
 	@Test

releaser-core/src/test/java/releaser/internal/git/ProjectGitHandlerTests.java

@@ -184,6 +184,19 @@ public class ProjectGitHandlerTests {
 		then(this.gitRepo).should().checkout("Finchley");
 	}
 
+	@Test
+	public void should_check_out_a_branch_if_it_exists_when_cloning_from_org_and_its_a_release_train_version_with_release_train_branch_set() {
+		this.properties.getGit().setReleaseTrainBranch("2020.0.x");
+		this.properties.getFixedVersions().put("spring-cloud-release", "2020.0.0-M1");
+		given(this.gitRepo.hasBranch(anyString())).willReturn(false);
+		given(this.gitRepo.hasBranch("2020.0.x")).willReturn(true);
+
+		this.updater.cloneProjectFromOrg("spring-cloud-release");
+
+		then(this.gitRepo).should().checkout("2020.0.x");
+		this.properties.getGit().setReleaseTrainBranch(null);
+	}
+
 	@Test
 	public void should_not_check_out_a_branch_if_it_does_not_exist_when_cloning_and_guessing_branch() {
 		given(this.gitRepo.hasBranch(anyString())).willReturn(true);