collects files of given extensions in a directory tree.
startDir is the directory where to start collecting;
extensionL provides a list of file extensions to collect;
absolute indicates whether to use absolte filenames;
follow indicates whether to follow symbolic links (Unix only);
exclude is a regular expression string; directories matching
this regex are skipped.
finds the common prefix for the paths given in *paths.
Note that this function, unlike its counterpart in os.path, does a
os.path.normpath prior to the comparison so that
"/home/user/../../vitaldata" and "/home/user" do _not_ have a common prefix!
Note also that "/home/user" does not have a common prefix with "home/user",
i.e., relative and absolute paths are distinguished.
finds the common postfix for the paths given in *paths.
Note that a trailing os.sep character will spoil the comparison, i.e.,
"/usr/data/" will not have a common postfix with "/usr/local/data"!
copies files given in the list of file names fileNameL to the target
directory given in targetDir. If prompt is set to 1, a console dialog
is popped up in case a file is about to be overwritten.
strips a prefix off a path. This will shorten path by prefixPath,
if the latter is indeed a prefix of the former. Otherwise, path is
returned unchanged.