NewVolumeLabels.numComponents method. Fix to fixlabels.saveLabelFile -

currently dirname has to be output as the first line, as loadLabelFile will
crash on files which don't have it.

fsl/data/fixlabels.py

@@ -237,7 +237,8 @@ def saveLabelFile(allLabels,
 
     :arg dirname:      If provided, is output as the first line of the file.
                        Intended to be a relative path to the MELODIC analysis
-                       directory with which this label file is associated.
+                       directory with which this label file is associated. If
+                       not provided, a ``'.'`` is output as the first line.
 
     :arg listBad:      If ``True`` (the default), the last line of the file
                        will contain a comma separated list of components which
@@ -251,8 +252,10 @@ def saveLabelFile(allLabels,
     noisyComps = []
 
     # The first line - the melodic directory name
-    if dirname is not None:
-        lines.append(dirname)
+    if dirname is None:
+        dirname = '.'
+
+    lines.append(dirname)
 
     # A line for each component
     for i, labels in enumerate(allLabels):

fsl/data/volumelabels.py

@@ -38,6 +38,7 @@ class VolumeLabels(notifier.Notifier):
        clear
        load
        save
+       numComponents
        hasLabel
        hasComponent
        getLabels
@@ -95,6 +96,12 @@ class VolumeLabels(notifier.Notifier):
 
         self.clear()
 
+    def numComponents(self):
+        """Returns the number of components (a.k.a. volumes) that this
+        ``VolumeLabels`` instance is managing.
+        """
+        return self.__ncomps
+
 
     def getDisplayLabel(self, label):
         """Returns the display name for the given label. """