Backport the use of hardlink instead of file copy

api/maven-api-core/src/main/java/org/apache/maven/api/JavaPathType.java

@@ -281,7 +281,7 @@ final String[] format(String moduleName, Iterable<? extends Path> paths) {
      */
     @Override
     public String toString() {
-        return "PathType[" + id() + "]";
+        return "PathType[" + id() + ']';
     }
 
     /**
@@ -325,7 +325,7 @@ public JavaPathType rawType() {
          */
         @Override
         public String id() {
-            return JavaPathType.this.name() + ":" + moduleName;
+            return JavaPathType.this.name() + ':' + moduleName;
         }
 
         /**
@@ -405,7 +405,7 @@ public boolean equals(Object obj) {
         @Nonnull
         @Override
         public String toString() {
-            return "PathType[" + id() + "]";
+            return "PathType[" + id() + ']';
         }
     }
 }

api/maven-api-core/src/main/java/org/apache/maven/api/package-info.java

@@ -119,9 +119,9 @@
  *
  * <p><dfn>Project aggregation</dfn> allows building several projects together. This is only
  * for projects that are built, hence available on the file system. One project,
- * called the <dfn>aggregator project</dfn> lists one or more <dfn>modules</dfn>
+ * called the <dfn>aggregator project</dfn> lists one or more <dfn>sub-projects</dfn>
  * which are relative pointers on the file system to other projects. This is done using
- * the {@code /project/modules/module} elements of the POM in the aggregator project.
+ * the {@code /project/subprojects/subproject} elements of the POM in the aggregator project.
  * Note that the aggregator project is required to have a {@code pom} packaging.</p>
  *
  * <p><dfn>Project inheritance</dfn> defines a parent-child relationship between projects.

impl/maven-core/src/main/java/org/apache/maven/ReactorReader.java

@@ -453,15 +453,29 @@ private void installIntoProjectLocalRepository(Artifact artifact) {
         Path target = getArtifactPath(
                 artifact.getGroupId(), artifact.getArtifactId(), artifact.getVersion(), classifier, extension);
         try {
-            LOGGER.info("Copying {} to project local repository", artifact);
-            Files.createDirectories(target.getParent());
-            Files.copy(
-                    artifact.getPath(),
-                    target,
-                    StandardCopyOption.REPLACE_EXISTING,
-                    StandardCopyOption.COPY_ATTRIBUTES);
+            // Log nothing as creating links should be very fast.
+            Path source = artifact.getPath();
+            if (!(Files.isRegularFile(target) && Files.isSameFile(source, target))) {
+                Files.createDirectories(target.getParent());
+                try {
+                    Files.deleteIfExists(target);
+                    Files.createLink(target, source);
+                } catch (UnsupportedOperationException | IOException suppressed) {
+                    LOGGER.info("Copying {} to project local repository.", artifact);
+                    try {
+                        Files.copy(
+                                source,
+                                target,
+                                StandardCopyOption.REPLACE_EXISTING,
+                                StandardCopyOption.COPY_ATTRIBUTES);
+                    } catch (IOException e) {
+                        e.addSuppressed(suppressed);
+                        throw e;
+                    }
+                }
+            }
         } catch (IOException e) {
-            LOGGER.error("Error while copying artifact to project local repository", e);
+            LOGGER.error("Error while copying artifact " + artifact + " to project local repository.", e);
         }
     }
 
@@ -481,9 +495,11 @@ private Path getArtifactPath(
                 .resolve(artifactId)
                 .resolve(version)
                 .resolve(artifactId
-                        + "-" + version
+                        + '-'
+                        + version
                         + (classifier != null && !classifier.isEmpty() ? "-" + classifier : "")
-                        + "." + extension);
+                        + '.'
+                        + extension);
     }
 
     private Path getProjectLocalRepo() {