Fix null credentialsId passed to GitSCM when authentication is userna…

…me/password or the StandardUsernameCredential provided by the BitbucketAuthenticator is null.

src/main/java/com/cloudbees/jenkins/plugins/bitbucket/BitbucketSCMSource.java

@@ -48,6 +48,7 @@
 import com.cloudbees.jenkins.plugins.bitbucket.server.client.repository.BitbucketServerRepository;
 import com.cloudbees.plugins.credentials.CredentialsNameProvider;
 import com.cloudbees.plugins.credentials.common.StandardCredentials;
+import com.cloudbees.plugins.credentials.common.StandardUsernameCredentials;
 import com.damnhandy.uri.template.UriTemplate;
 import com.fasterxml.jackson.databind.util.StdDateFormat;
 import edu.umd.cs.findbugs.annotations.CheckForNull;
@@ -66,6 +67,7 @@
 import hudson.model.Items;
 import hudson.model.TaskListener;
 import hudson.plugins.git.GitSCM;
+import hudson.plugins.git.extensions.GitSCMExtension;
 import hudson.scm.SCM;
 import hudson.security.AccessControlled;
 import hudson.util.FormFillFailure;
@@ -1000,12 +1002,32 @@ private BitbucketCommit findPRDestinationCommit(BitbucketPullRequest pr, TaskLis
     public SCM build(SCMHead head, SCMRevision revision) {
         initCloneLinks();
 
-        boolean sshAuth = traits.stream()
-                .anyMatch(SSHCheckoutTrait.class::isInstance);
+        String scmCredentialsId = credentialsId;
 
         BitbucketAuthenticator authenticator = authenticator();
-        return new BitbucketGitSCMBuilder(this, head, revision, null)
-                .withExtension(new GitClientAuthenticatorExtension(authenticator == null || sshAuth ? null : authenticator.getCredentialsForSCM()))
+        GitSCMExtension scmExtension;
+        if (authenticator != null) {
+            boolean sshAuth = traits.stream()
+                    .anyMatch(SSHCheckoutTrait.class::isInstance);
+            if (sshAuth) {
+                // trait will do the magic
+                scmCredentialsId = null;
+                scmExtension = new GitClientAuthenticatorExtension(null);
+            } else {
+                StandardUsernameCredentials scmCredentials = authenticator.getCredentialsForSCM();
+                // extension overrides the configured credentialsId with a custom StandardUsernameCredentials provided by the Authenticator
+                scmExtension = new GitClientAuthenticatorExtension(scmCredentials);
+                if (scmCredentials != null) {
+                    // will be overridden by git extension
+                    scmCredentialsId = null;
+                }
+            }
+        } else {
+            scmExtension = new GitClientAuthenticatorExtension(null);
+        }
+
+        return new BitbucketGitSCMBuilder(this, head, revision, scmCredentialsId)
+                .withExtension(scmExtension)
                 .withCloneLinks(primaryCloneLinks, mirrorCloneLinks)
                 .withTraits(traits)
                 .build();

src/main/java/com/cloudbees/jenkins/plugins/bitbucket/api/credentials/BitbucketUsernamePasswordAuthenticator.java

@@ -26,11 +26,7 @@
 package com.cloudbees.jenkins.plugins.bitbucket.api.credentials;
 
 import com.cloudbees.jenkins.plugins.bitbucket.api.BitbucketAuthenticator;
-import com.cloudbees.plugins.credentials.CredentialsScope;
-import com.cloudbees.plugins.credentials.common.StandardUsernameCredentials;
 import com.cloudbees.plugins.credentials.common.StandardUsernamePasswordCredentials;
-import com.cloudbees.plugins.credentials.impl.UsernamePasswordCredentialsImpl;
-import hudson.model.Descriptor.FormException;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import org.apache.http.HttpHost;
@@ -79,13 +75,4 @@ public void configureContext(HttpClientContext context, HttpHost host) {
         context.setAuthCache(authCache);
     }
 
-    @Override
-    public StandardUsernameCredentials getCredentialsForSCM() {
-        try {
-            return new UsernamePasswordCredentialsImpl(
-                    CredentialsScope.GLOBAL, getId(), null, httpCredentials.getUserName(), httpCredentials.getPassword());
-        } catch (FormException e) {
-            throw new RuntimeException(e);
-        }
-    }
 }