Add configuration to be able to use the plugin without scm info in pom

src/main/java/org/codehaus/mojo/build/AbstractScmMojo.java

@@ -135,6 +135,20 @@ public abstract class AbstractScmMojo extends AbstractMojo {
     @Component
     protected ScmManager scmManager;
 
+    /**
+     * Ignore error when scm url from pom is empty and replace by scm:scmProvider {@link #scmProvider}
+     * @since 3.2.1
+     */
+    @Parameter(property = "maven.buildNumber.ignoreEmptyScmUrl", defaultValue = "false")
+    private boolean ignoreEmptyScmUrl;
+
+    /**
+     * When scm url is empty, scm provider is needed {@link #ignoreEmptyScmUrl}
+     * @since 3.2.1
+     */
+    @Parameter(property = "maven.buildNumber.scmProvider", defaultValue = "git")
+    private String scmProvider;
+
     /**
      * Maven Security Dispatcher
      *
@@ -176,8 +190,9 @@ private String decrypt(String str, String server) {
     }
 
     protected ScmRepository getScmRepository() throws ScmException {
+        String repoUrl = !StringUtils.isBlank(this.scmConnectionUrl) ? scmConnectionUrl : scmDeveloperConnectionUrl;
         ScmRepository repository = scmManager.makeScmRepository(
-                !StringUtils.isBlank(this.scmConnectionUrl) ? scmConnectionUrl : scmDeveloperConnectionUrl);
+                StringUtils.isBlank(repoUrl) ? (ignoreEmptyScmUrl ? "scm:" + scmProvider + ":" : "") : repoUrl);
 
         ScmProviderRepository scmRepo = repository.getProviderRepository();
 

src/site/fml/faq.fml

@@ -25,6 +25,8 @@ under the License.
       <answer>
         <p>Yes, set the plugin parameter </p> <source> &lt;revisionOnScmFailure&gt;</source> <p>to prevent 
         the plugin from throwing an exception if SCM information is not found.</p>
+        <p>The other option is to use <source>-Dmaven.buildNumber.ignoreEmptyScmUrl=true -Dmaven.buildNumber.scmProvider=git/svn/</source>
+        Default is git</p>
       </answer>
     </faq>
 

src/test/java/org/codehaus/mojo/build/it/CreateMetadataMojoTest.java

@@ -55,4 +55,19 @@ public void testBasicJsonConfiguration() throws Exception {
         Assert.assertTrue(new File(testDir, "target/generated/build-metadata/build.properties").exists());
         Assert.assertTrue(new File(testDir, "target/classes/build.properties").exists());
     }
+
+    @Test
+    public void testBasicConfigurationNoScm() throws Exception {
+        File projDir = resources.getBasedir("create-metadata-it-no-scm");
+
+        MavenExecution mavenExec = maven.forProject(projDir);
+        MavenExecutionResult result = mavenExec.withCliOption("-e").execute("clean", "test");
+        result.assertErrorFreeLog();
+
+        File testDir = result.getBasedir();
+        Assert.assertTrue(new File(testDir, "target/file1.properties").exists());
+        Assert.assertTrue(new File(testDir, "target/xxx/file1.properties").exists());
+        Assert.assertTrue(new File(testDir, "target/generated/build-metadata/build.properties").exists());
+        Assert.assertTrue(new File(testDir, "target/classes/build.properties").exists());
+    }
 }

src/test/projects/create-metadata-it-no-scm/pom.xml

@@ -0,0 +1,42 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>org.codehaus.mojo.it</groupId>
+  <artifactId>build-metadata-it</artifactId>
+  <version>1.0-SNAPSHOT</version>
+
+  <build>
+
+    <defaultGoal>package</defaultGoal>
+
+    <plugins>
+      <plugin>
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>buildnumber-maven-plugin</artifactId>
+        <version>${it-plugin.version}</version>
+        <executions>
+          <execution>
+            <id>useLastCommittedRevision</id>
+            <goals>
+              <goal>create-metadata</goal>
+            </goals>
+            <configuration>
+              <ignoreEmptyScmUrl>true</ignoreEmptyScmUrl>
+              <revisionOnScmFailure>UNKNOWN</revisionOnScmFailure>
+              <!-- see outputDirectory + outputName for the default outputFile -->
+              <outputFiles>
+                <outputFile>${project.build.directory}/file1.properties</outputFile>
+                <outputFile>${project.build.directory}/xxx/file1.properties</outputFile>
+              </outputFiles>
+              <addOutputDirectoryToResources>true</addOutputDirectoryToResources>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+
+  </build>
+
+</project>