Allow to amend commits with JGit CLI

Change-Id: I0e8d365b56e079ac4ccece7fcf80ea140c319c78

org.eclipse.jgit.pgm/resources/org/eclipse/jgit/pgm/CLIText.properties

@@ -141,6 +141,7 @@ usage_CommandLineClientForamazonsS3Service=Command line client for Amazon's S3 s
 usage_CommitAuthor=Override the author name used in the commit. You can use the standard A U Thor <author@example.com> format.
 usage_CommitMessage=Use the given <msg> as the commit message
 usage_CommitOnly=commit specified paths only
+usage_CommitAmend=Amend the tip of the current branch
 usage_CommitPaths=see --only
 usage_CreateABareRepository=Create a bare repository
 usage_CreateATag=Create a tag

org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Commit.java

@@ -67,6 +67,9 @@ class Commit extends TextBuiltin {
 	@Option(name = "--only", aliases = { "-o" }, usage = "usage_CommitOnly")
 	private boolean only;
 
+	@Option(name = "--amend", usage = "usage_CommitAmend")
+	private boolean amend;
+
 	@Argument(metaVar = "metaVar_commitPaths", usage = "usage_CommitPaths")
 	private List<String> paths = new ArrayList<String>();
 
@@ -83,6 +86,7 @@ class Commit extends TextBuiltin {
 		if (!paths.isEmpty())
 			for (String p : paths)
 				commitCmd.setOnly(p);
+		commitCmd.setAmend(amend);
 		Ref head = db.getRef(Constants.HEAD);
 		RevCommit commit = commitCmd.call();