feat: accept customized Maven user settings file and local repository. (#184)

## Description

feat: accept customized Maven user settings file and local repository.

**Related issue (if any):**
redhat-developer/intellij-dependency-analytics#218

intellij-dependency-analytics PR:
redhat-developer/intellij-dependency-analytics#220

## Checklist

- [x] I have followed this repository's contributing guidelines.
- [x] I will adhere to the project's code of conduct.

---------

Signed-off-by: Chao Wang <chaowan@redhat.com>

Author: soul2zimate

README.md

@@ -328,6 +328,9 @@ System.setProperty("EXHORT_PYTHON_PATH", "/path/to/python");
 System.setProperty("EXHORT_PIP_PATH", "/path/to/pip");
 // Configure proxy for all requests
 System.setProperty("EXHORT_PROXY_URL", "http://proxy.example.com:8080");
+// Configure Maven settings and repository
+System.setProperty("EXHORT_MVN_USER_SETTINGS", "/path/to/custom/settings.xml");
+System.setProperty("EXHORT_MVN_LOCAL_REPO", "/path/to/custom/local/repository");
 ```
 
 > Environment variables takes precedence.
@@ -436,6 +439,47 @@ following keys for setting custom paths for the said executables.
 
 </table>
 
+#### Maven Configuration
+
+You can customize Maven behavior by setting additional environment variables or Java properties:
+
+<table>
+<tr>
+<th>Configuration</th>
+<th>Environment Variable</th>
+<th>Description</th>
+<th>Default</th>
+</tr>
+<tr>
+<td>Maven User Settings</td>
+<td>EXHORT_MVN_USER_SETTINGS</td>
+<td>Path to custom Maven settings.xml file</td>
+<td><em>Uses Maven's default settings</em></td>
+</tr>
+<tr>
+<td>Maven Local Repository</td>
+<td>EXHORT_MVN_LOCAL_REPO</td>
+<td>Path to custom Maven local repository directory</td>
+<td><em>Uses Maven's default local repository</em></td>
+</tr>
+</table>
+
+**Examples:**
+
+Using environment variables:
+```bash
+export EXHORT_MVN_USER_SETTINGS=/home/user/.m2/custom-settings.xml
+export EXHORT_MVN_LOCAL_REPO=/home/user/custom-maven-repo
+```
+
+Using Java properties:
+```java
+System.setProperty("EXHORT_MVN_USER_SETTINGS", "/home/user/.m2/custom-settings.xml");
+System.setProperty("EXHORT_MVN_LOCAL_REPO", "/home/user/custom-maven-repo");
+```
+
+> Environment variables take precedence over Java properties.
+
 #### Match Manifest Versions Feature
 
 ##### Background

src/main/java/com/redhat/exhort/providers/JavaMavenProvider.java

@@ -65,28 +65,23 @@ public JavaMavenProvider(Path manifest) {
 
   @Override
   public Content provideStack() throws IOException {
-    var mvnCleanCmd =
-        new String[] {mvnExecutable, "clean", "-f", manifest.toString(), "--batch-mode", "-q"};
+    var mvnCleanCmd = buildMvnCommandArgs("clean", "-f", manifest.toString(), "--batch-mode", "-q");
     var mvnEnvs = getMvnExecEnvs();
     // execute the clean command
-    Operations.runProcess(manifest.getParent(), mvnCleanCmd, mvnEnvs);
+    Operations.runProcess(manifest.getParent(), mvnCleanCmd.toArray(String[]::new), mvnEnvs);
     // create a temp file for storing the dependency tree in
     var tmpFile = Files.createTempFile("exhort_dot_graph_", null);
     // the tree command will build the project and create the dependency tree in the temp file
     var mvnTreeCmd =
-        new ArrayList<String>() {
-          {
-            add(mvnExecutable);
-            add("org.apache.maven.plugins:maven-dependency-plugin:3.6.0:tree");
-            add("-Dverbose");
-            add("-DoutputType=text");
-            add(String.format("-DoutputFile=%s", tmpFile.toString()));
-            add("-f");
-            add(manifest.toString());
-            add("--batch-mode");
-            add("-q");
-          }
-        };
+        buildMvnCommandArgs(
+            "org.apache.maven.plugins:maven-dependency-plugin:3.6.0:tree",
+            "-Dverbose",
+            "-DoutputType=text",
+            String.format("-DoutputFile=%s", tmpFile.toString()),
+            "-f",
+            manifest.toString(),
+            "--batch-mode",
+            "-q");
     // if we have dependencies marked as ignored, exclude them from the tree command
     var ignored =
         getDependencies(manifest).stream()
@@ -133,18 +128,17 @@ public Content provideComponent() throws IOException {
   private Content generateSbomFromEffectivePom() throws IOException {
     var tmpEffPom = Files.createTempFile("exhort_eff_pom_", ".xml");
     var mvnEffPomCmd =
-        new String[] {
-          mvnExecutable,
-          "clean",
-          "help:effective-pom",
-          String.format("-Doutput=%s", tmpEffPom.toString()),
-          "-f",
-          manifest.toString(),
-          "--batch-mode",
-          "-q"
-        };
+        buildMvnCommandArgs(
+            "clean",
+            "help:effective-pom",
+            String.format("-Doutput=%s", tmpEffPom.toString()),
+            "-f",
+            manifest.toString(),
+            "--batch-mode",
+            "-q");
     // execute the effective pom command
-    Operations.runProcess(manifest.getParent(), mvnEffPomCmd, getMvnExecEnvs());
+    Operations.runProcess(
+        manifest.getParent(), mvnEffPomCmd.toArray(String[]::new), getMvnExecEnvs());
     if (debugLoggingIsNeeded()) {
       String CaEffectivePoM = Files.readString(tmpEffPom);
       log.info(
@@ -345,6 +339,28 @@ Map<String, String> getMvnExecEnvs() {
     return null;
   }
 
+  private List<String> buildMvnCommandArgs(String... baseArgs) {
+    List<String> args = new ArrayList<>();
+    args.add(mvnExecutable);
+
+    var userSettingsFile = Operations.getMavenConfig("USER_SETTINGS");
+    if (userSettingsFile != null) {
+      args.add("-s");
+      args.add(userSettingsFile);
+    }
+
+    var localRepository = Operations.getMavenConfig("LOCAL_REPO");
+    if (localRepository != null) {
+      args.add("-Dmaven.repo.local=" + localRepository);
+    }
+
+    for (String arg : baseArgs) {
+      args.add(arg);
+    }
+
+    return args;
+  }
+
   // NOTE if we want to include "scope" tags in ignore,
   // add property here and a case in the start-element-switch in the getIgnored method
 

src/main/java/com/redhat/exhort/tools/Operations.java

@@ -316,6 +316,17 @@ public static boolean getWrapperPreference(String name) {
     return Environment.get("EXHORT_PREFER_" + name.toUpperCase() + "W") != null;
   }
 
+  /**
+   * Retrieves a Maven configuration value from an environment variable.
+   *
+   * @param configName the configuration name (e.g., "USER_SETTINGS", "LOCAL_REPO")
+   * @return the configuration value if set and not blank, null otherwise
+   */
+  public static String getMavenConfig(String configName) {
+    String configValue = Environment.get("EXHORT_MVN_" + configName);
+    return (configValue != null && !configValue.isBlank()) ? configValue : null;
+  }
+
   /**
    * Attempts to retrieve the root directory of a Git repository for the given working directory.
    *