git-cvsimport-script: move working directory forward

If HEAD happened to point to a cvs branch, move the
working directory forward to the tip of the branch.
Additionally, if master and "origin" are equal,
move master forward to new origin first.

git-cvsimport-script

@@ -372,6 +372,7 @@ chdir($git_tree);
 
 my $last_branch = "";
 my $orig_branch = "";
+my $forward_master = 0;
 my %branch_date;
 
 my $git_dir = $ENV{"GIT_DIR"} || ".git";
@@ -403,6 +404,21 @@ unless(-d $git_dir) {
 		$last_branch = "master";
 	}
 	$orig_branch = $last_branch;
+	if (-f "$git_dir/CVS2GIT_HEAD") {
+		die <<EOM;
+CVS2GIT_HEAD exists.
+Make sure your working directory corresponds to HEAD and remove CVS2GIT_HEAD.
+You may need to run
+
+    git-read-tree -m -u CVS2GIT_HEAD HEAD
+EOM
+	}
+	system('cp', "$git_dir/HEAD", "$git_dir/CVS2GIT_HEAD");
+
+	$forward_master =
+	    $opt_o ne 'master' && -f "$git_dir/refs/heads/master" &&
+	    system('cmp', '-s', "$git_dir/refs/heads/master", 
+				"$git_dir/refs/heads/$opt_o") == 0;
 
 	# populate index
 	system('git-read-tree', $last_branch);
@@ -695,9 +711,19 @@ while(<CVS>) {
 
 unlink($git_index);
 
+if (defined $orig_git_index) {
+	$ENV{GIT_INDEX_FILE} = $orig_git_index;
+} else {
+	delete $ENV{GIT_INDEX_FILE};
+}
+
 # Now switch back to the branch we were in before all of this happened
 if($orig_branch) {
 	print "DONE\n" if $opt_v;
+	system("cp","$git_dir/refs/heads/$opt_o","$git_dir/refs/heads/master")
+		if $forward_master;
+	system('git-read-tree', '-m', '-u', 'CVS2GIT_HEAD', 'HEAD');
+	die "read-tree failed: $?\n" if $?;
 } else {
 	$orig_branch = "master";
 	print "DONE; creating $orig_branch branch\n" if $opt_v;
@@ -705,11 +731,7 @@ if($orig_branch) {
 		unless -f "$git_dir/refs/heads/master";
 	unlink("$git_dir/HEAD");
 	symlink("refs/heads/$orig_branch","$git_dir/HEAD");
-	if (defined $orig_git_index) {
-	    $ENV{GIT_INDEX_FILE} = $orig_git_index;
-	} else {
-	    delete $ENV{GIT_INDEX_FILE};
-	}
 	system('git checkout');
 	die "checkout failed: $?\n" if $?;
 }
+unlink("$git_dir/CVS2GIT_HEAD");