use the actual Commit object instead of its id in the Status, small doc fixes

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

 package de.uni_passau.fim.seibt.gitwrapper.repo;
 
+import java.io.StringWriter;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.Collections;
@@ -21,10 +22,10 @@ public class Status {
     /**
      * The commit, this {@link Status} is based on.
      */
-    public final String id;
+    public final Commit commit;
 
     /**
-     * A map of files which were changed since the last commit (with id {@link #id}) and their status codes.
+     * A map of files which were changed since the last {@link #commit} and their status codes.
      */
     public final Map<Path, String> changed;
 
@@ -34,18 +35,20 @@ public class Status {
     public final Map<Path, String> unmerged;
 
     /**
-     * @param id       the commit id
+     * Constructs a new {@link Status}.
+     *
+     * @param commit   the current HEAD {@link Commit} at the time this {@link Status} is constructed
      * @param changed  a map of changed files and heir status codes
      * @param unmerged a map of unmerged files an their status code.
      */
-    private Status(String id, Map<Path, String> changed, Map<Path, String> unmerged) {
-        this.id = id;
+    private Status(Commit commit, Map<Path, String> changed, Map<Path, String> unmerged) {
+        this.commit = commit;
         this.changed = Collections.unmodifiableMap(changed);
         this.unmerged = Collections.unmodifiableMap(unmerged);
     }
 
     /**
-     * Checks, if <code>this</code> represents a clean repository.
+     * Returns whether this {@link Status} represents a clean repository.
      *
      * @return <code>true</code>, if the repository state is clean and has uncommitted changes.
      */
@@ -54,7 +57,7 @@ public class Status {
     }
 
     /**
-     * Checks, if <code>this</code> has unmerged files.
+     * Returns whether this {@link Status} has unmerged files.
      *
      * @return <code>true</code>, if there are unmerged files
      */
@@ -66,7 +69,7 @@ public class Status {
     public String toString() {
         String out = "";
         if (isClean()) {
-            out = "Clean working directory on commit " + id + "\n";
+            out = "Clean working directory on commit " + commit + "\n";
         } else {
             if (!unmerged.isEmpty()) {
                 out = "Unmerged files:";
@@ -105,6 +108,6 @@ public class Status {
             }
         }
 
-        return repo.getCurrentHEAD().map(head -> new Status(head.id, changed, unmerged));
+        return repo.getCurrentHEAD().map(head -> new Status(head, changed, unmerged));
     }
 }