I’d like to update an old a code which checkouts a tag in a repository. It’s very slow but it turns out there’s no need to do a real checkout but only to have a read-only snapshot.

The original code is:

import java.io.File;

import org.apache.maven.scm.ScmException;
import org.apache.maven.scm.ScmFileSet;
import org.apache.maven.scm.ScmTag;
import org.apache.maven.scm.ScmVersion;
import org.apache.maven.scm.manager.BasicScmManager;
import org.apache.maven.scm.manager.ScmManager;
import org.apache.maven.scm.provider.git.jgit.JGitScmProvider;
import org.apache.maven.scm.repository.ScmRepository;

public class TestSCM {
    public static void main(String[] args) throws ScmException {
        ScmManager scmManager = new BasicScmManager();
        scmManager.setScmProvider("git", new JGitScmProvider(null));
        File tmpDir = new File(System.getProperty("java.io.tmpdir"));
        File checkoutDirectory = new File(tmpDir, "test_checkout");
        if (!checkoutDirectory.exists()) {
            checkoutDirectory.mkdir();
        }
        ScmVersion scmVersion = new ScmTag("I20231202-0500");
        ScmRepository repository = scmManager
                .makeScmRepository("scm:git:https://github.com/eclipse-jdt/eclipse.jdt.core.git");

        scmManager.checkOut(repository, new ScmFileSet(checkoutDirectory), scmVersion);
    }
}

I replaced checkOut with export:

import java.io.File;

import org.apache.maven.scm.ScmException;
import org.apache.maven.scm.ScmFileSet;
import org.apache.maven.scm.ScmTag;
import org.apache.maven.scm.ScmVersion;
import org.apache.maven.scm.manager.BasicScmManager;
import org.apache.maven.scm.manager.ScmManager;
import org.apache.maven.scm.provider.git.jgit.JGitScmProvider;
import org.apache.maven.scm.repository.ScmRepository;

public class TestSCM {
    public static void main(String[] args) throws ScmException {
        ScmManager scmManager = new BasicScmManager();
        scmManager.setScmProvider("git", new JGitScmProvider(null));
        File tmpDir = new File(System.getProperty("java.io.tmpdir"));
        File checkoutDirectory = new File(tmpDir, "test_checkout");
        if (!checkoutDirectory.exists()) {
            checkoutDirectory.mkdir();
        }
        ScmVersion scmVersion = new ScmTag("I20231202-0500");
        ScmRepository repository = scmManager
                .makeScmRepository("scm:git:https://github.com/eclipse-jdt/eclipse.jdt.core.git");

        scmManager.export(repository, new ScmFileSet(checkoutDirectory), scmVersion);
    }
}

It seems to be unimplemented:

java.lang.UnsupportedOperationException: getExportCommand
    at org.apache.maven.scm.provider.git.jgit.JGitScmProvider.getExportCommand(JGitScmProvider.java:125)
    at org.apache.maven.scm.provider.git.AbstractGitScmProvider.export(AbstractGitScmProvider.java:210)
    at org.apache.maven.scm.provider.AbstractScmProvider.export(AbstractScmProvider.java:642)
    at org.apache.maven.scm.provider.AbstractScmProvider.export(AbstractScmProvider.java:624)
    at org.apache.maven.scm.manager.AbstractScmManager.export(AbstractScmManager.java:458)

I use these dependencies:

<dependency>
    <groupId>org.apache.maven.scm</groupId>
    <artifactId>maven-scm-api</artifactId>
    <version>2.1.0</version>
</dependency>
<dependency>
    <groupId>org.apache.maven.scm</groupId>
    <artifactId>maven-scm-provider-jgit</artifactId>
    <version>2.1.0</version>
</dependency>