Empty prefix setting should not keep the leading "."

Resolves #101

Author: ktoso

src/main/java/pl/project13/maven/git/GitCommitIdMojo.java

@@ -302,7 +302,9 @@ public void execute() throws MojoExecutionException {
 
     try {
       properties = initProperties();
-      prefixDot = prefix + ".";
+
+      String trimmedPrefix = prefix.trim();
+      prefixDot = trimmedPrefix.equals("") ? "" : trimmedPrefix + ".";
 
       loadGitData(properties);
       loadBuildTimeData(properties);

src/test/java/pl/project13/maven/git/GitCommitIdMojoTest.java

@@ -111,6 +111,24 @@ public void shouldExcludeAsConfiguredProperties() throws Exception {
     verify(mojo).putGitDescribe(any(Properties.class), any(Repository.class));
   }
 
+
+  @Test
+  public void shouldHaveNoPrefixWhenConfiguredPrefixIsEmptyStringAsConfiguredProperties() throws Exception {
+    // given
+    mojo.setPrefix("");
+
+    // when
+    mojo.execute();
+
+    // then
+    Properties properties = mojo.getProperties();
+
+    // explicitly excluded
+    assertThat(properties).satisfies(new DoesNotContainKeyCondition("git.remote.origin.url"));
+    assertThat(properties).satisfies(new DoesNotContainKeyCondition(".remote.origin.url"));
+    assertThat(properties).satisfies(new ContainsKeyCondition("remote.origin.url"));
+  }
+
   @Test
   public void shouldSkipDescribeWhenConfiguredToDoSo() throws Exception {
     // given