Merge pull request #342 from TheSnoozer/master

fix  #341 (NullPointerException at pl.project13.jgit.dummy.DatedRevTag) and adding readme section about mvn install/deploy

Author: TheSnoozer

README.md

@@ -957,6 +957,12 @@ Example:
 If you are using the maven build with [Maven's Plugin Prefix Resolution](https://maven.apache.org/guides/introduction/introduction-to-plugin-prefix-mapping.html) (e.g. `mvn somePrefix:goal`) please note that this currently seems to be [not supported by maven](https://issues.apache.org/jira/browse/MNG-6260).
 Instead of using the Plugin Prefix Resolution add an execution tag that calls the desired goal of the plugin within a normal maven life cycle (e.g. `mvn clean package`).
 
+Generated properties are not being used in install and/or deploy
+-------------------------------
+If you try to use generated properties like ${git.commit.id} alongside with your artificat finalName you will soon notice that those properties are not being used in install and/or deploy. This specific behaviour is basically not intended / not supported by maven-install-plugin and/or maven-deploy-plugin (https://issues.apache.org/jira/browse/MINSTALL-1 / https://issues.apache.org/jira/browse/MDEPLOY-93). The naming format in the remote repo seems always $artifactId-$version-$classifier *by default* and thus any generated property will not end up inside the artifact being installed/deployed. If you for whatever reason still want to have something special you may want to [checkout a full workaround](https://github.com/ktoso/maven-git-commit-id-plugin/issues/256#issuecomment-321476196) that uses a specific configuration of `install-file` / `deploy-file`.
+
+As a general note also ensure to use `mvn clean deploy` instead of `mvn deploy:deploy` (or you run into  https://issues.apache.org/jira/browse/MNG-6260) and ensure to set `<injectAllReactorProjects>true</injectAllReactorProjects>` inside the plugin's config.
+
 How to contribute to the project
 -------------------------------
 In general pull requests and support for open issues is always welcome!

src/main/java/pl/project13/jgit/dummy/DatedRevTag.java

@@ -29,7 +29,7 @@ public class DatedRevTag {
   public final DateTime date;
 
   public DatedRevTag(RevTag tag) {
-    this(tag.getId(), tag.getTagName(), new DateTime(tag.getTaggerIdent().getWhen()));
+    this(tag.getId(), tag.getTagName(), (tag.getTaggerIdent() != null) ? new DateTime(tag.getTaggerIdent().getWhen()) : DateTime.now().minusYears(1900));
   }
 
   public DatedRevTag(AnyObjectId id, String tagName) {