feat: update var names and add missing docs.

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

@@ -343,13 +343,13 @@ private List<String> buildMvnCommandArgs(String... baseArgs) {
     List<String> args = new ArrayList<>();
     args.add(mvnExecutable);
 
-    var userSettingsFile = Operations.getMavenConfig("USER_SETTINGS_FILE");
+    var userSettingsFile = Operations.getMavenConfig("USER_SETTINGS");
     if (userSettingsFile != null) {
       args.add("-s");
       args.add(userSettingsFile);
     }
 
-    var localRepository = Operations.getMavenConfig("LOCAL_REPOSITORY");
+    var localRepository = Operations.getMavenConfig("LOCAL_REPO");
     if (localRepository != null) {
       args.add("-Dmaven.repo.local=" + localRepository);
     }

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

@@ -319,7 +319,7 @@ public static boolean getWrapperPreference(String name) {
   /**
    * Retrieves a Maven configuration value from an environment variable.
    *
-   * @param configName the configuration name (e.g., "USER_SETTINGS_FILE", "LOCAL_REPOSITORY")
+   * @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) {