add a method for retrieving the paths affected by a commit

src/de/uni_passau/fim/seibt/gitwrapper/repo/Commit.java

 package de.uni_passau.fim.seibt.gitwrapper.repo;
 
+import java.nio.file.Path;
 import java.time.Instant;
 import java.time.OffsetDateTime;
 import java.time.ZoneId;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Optional;
 import java.util.function.Function;
+import java.util.function.Supplier;
 import java.util.logging.Logger;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -73,6 +77,41 @@ public class Commit extends Reference {
         return res.map(toBoolean);
     }
 
+    /**
+     * Returns the paths that were affected by this {@link Commit}.
+     *
+     * @return optionally the {@link List} of {@link Path Paths}
+     */
+    public Optional<List<Path>> getAffectedPaths() {
+        Optional<ExecRes> res = git.exec(repo.getDir(), "show", "--name-only", "--pretty=format:", id);
+        Function<ExecRes, List<Path>> toPaths = execRes -> {
+            Supplier<String> errorMsg = () -> "Failed to determine the paths affected by '" + this + "'.";
+
+            if (git.failed(execRes)) {
+                LOG.warning(errorMsg);
+                return null;
+            }
+
+            String[] lines = execRes.getStdOutTrimmed().split("\\R");
+            List<Path> paths = new ArrayList<>();
+
+            for (String line : lines) {
+                Optional<Path> oPath = git.getPath(line);
+
+                if (oPath.isPresent()) {
+                    paths.add(oPath.get());
+                } else {
+                    LOG.warning(errorMsg);
+                    return null;
+                }
+            }
+
+            return paths;
+        };
+
+        return res.map(toPaths);
+    }
+
     /**
      * Returns the author of this commit.
      *