Add the --branch flag to the jgit clone command

--branch or -b allows the user to specify which branch to checkout after
clone.

Change-Id: Ie27533e5ecb43097862a8337a27a742b501e17a5

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

@@ -76,6 +76,7 @@ metaVar_author=AUTHOR
 metaVar_base=base
 metaVar_blameL=START,END
 metaVar_blameReverse=START..END
+metaVar_branchName=branch
 metaVar_bucket=BUCKET
 metaVar_command=command
 metaVar_commandDetail=DETAIL
@@ -116,6 +117,7 @@ mostCommonlyUsedCommandsAre=The most commonly used commands are:
 needApprovalToDestroyCurrentRepository=Need approval to destroy current repository
 noGitRepositoryConfigured=No Git repository configured.
 noSuchFile=no such file: {0}
+noSuchRemoteRef=no such remote ref: ''{0}''
 noTREESectionInIndex=no 'TREE' section in index
 nonFastForward=non-fast forward
 notABranch={0} is not a branch
@@ -274,5 +276,6 @@ usage_symbolicVersionForTheProject=Symbolic version for the project
 usage_tagMessage=tag message
 usage_updateRemoteRefsFromAnotherRepository=Update remote refs from another repository
 usage_useNameInsteadOfOriginToTrackUpstream=use <name> instead of 'origin' to track upstream
+usage_checkoutBranchAfterClone=checkout named branch instead of remotes's HEAD
 usage_viewCommitHistory=View commit history
 warningNoCommitGivenOnCommandLine=warning: No commit given on command line, assuming {0}

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

@@ -180,6 +180,7 @@ public class CLIText extends TranslationBundle {
 	/***/ public String needApprovalToDestroyCurrentRepository;
 	/***/ public String noGitRepositoryConfigured;
 	/***/ public String noSuchFile;
+	/***/ public String noSuchRemoteRef;
 	/***/ public String noTREESectionInIndex;
 	/***/ public String nonFastForward;
 	/***/ public String notABranch;

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

@@ -74,6 +74,9 @@ class Clone extends AbstractFetchCommand {
 	@Option(name = "--origin", aliases = { "-o" }, metaVar = "metaVar_remoteName", usage = "usage_useNameInsteadOfOriginToTrackUpstream")
 	private String remoteName = Constants.DEFAULT_REMOTE_NAME;
 
+	@Option(name = "--branch", aliases = { "-b" }, metaVar = "metaVar_branchName", usage = "usage_checkoutBranchAfterClone")
+	private String branch;
+
 	@Argument(index = 0, required = true, metaVar = "metaVar_uriish")
 	private String sourceUri;
 
@@ -117,8 +120,16 @@ class Clone extends AbstractFetchCommand {
 
 		saveRemote(uri);
 		final FetchResult r = runFetch();
-		final Ref branch = guessHEAD(r);
+		final Ref checkoutRef;
-		doCheckout(branch);
+		if (branch == null)
+			checkoutRef = guessHEAD(r);
+		else {
+			checkoutRef = r.getAdvertisedRef(Constants.R_HEADS + branch);
+			if (checkoutRef == null)
+				throw die(MessageFormat.format(CLIText.get().noSuchRemoteRef,
+						branch));
+		}
+		doCheckout(checkoutRef);
 	}
 
 	private void saveRemote(final URIish uri) throws URISyntaxException,