gstlal_inspiral_bank_splitter: standardize split bank filenames

gstlal-inspiral/bin/gstlal_inspiral_bank_splitter

@@ -248,7 +248,7 @@ for bank_count, (_, rows) in enumerate(outputrows, start=split_bin_start):
 		row.mtotal = row.mass1 + row.mass2
 
 	sngl_inspiral_table[:] = rows
-	output = datafind.T050017_filename(options.instrument, "%04d_GSTLAL_SPLIT_BANK" % bank_count, (0, 0), ".xml.gz", path = options.output_path)
+	output = datafind.T050017_filename(options.instrument, f"GSTLAL_SPLIT_BANK_{bank_count:04d}", (0, 0), ".xml.gz", path = options.output_path)
 	metadata[output] = rows
 	svd_dirs.append(output)
 	ligolw_utils.write_filename(xmldoc, output, verbose = options.verbose)
@@ -258,27 +258,22 @@ if options.bank_name:
 
 svd_groups = list(svd_bank.group(svd_dirs, options.num_banks))
 for n, svd in enumerate(svd_groups, start=svd_bin_start):
-	outdir = os.path.join(options.output_path, "%04d" % n)
-	try:
-		os.mkdir(outdir)
-	except OSError:
-		# svd directory already exists
-		pass
 	svd_mchirps = []
 	svd_durs = []
 	svd_bw = []
 	ref_hd = []
 	clipleft = options.overlap // 2
 	clipright = options.overlap // 2
-	for m, split_file in enumerate(svd):
+	for m, split_file in enumerate(svd, start=split_bin_start):
 		svd_mchirps.extend([r.mchirp for r in metadata[split_file][clipleft:-clipright]])
 		svd_durs.extend([r.template_duration for r in metadata[split_file][clipleft:-clipright]])
 		svd_bw.extend([r.bandwidth for r in metadata[split_file][clipleft:-clipright]])
-		outfile = os.path.join(outdir, os.path.split(split_file)[1])
+		outfile = datafind.T050017_filename(options.instrument, f"{n:04d}_GSTLAL_SPLIT_BANK_{m:04d}", (0, 0), ".xml.gz", path = options.output_path)
 		shutil.move(split_file, outfile)
 		xmldoc = ligolw_utils.load_url(outfile, contenthandler = LIGOLWContentHandler, verbose = options.verbose)
 		process = ligolw_process.register_to_xmldoc(xmldoc, program = "gstlal_inspiral_bank_splitter", paramdict = {"clipleft": clipleft, "clipright": clipright, "bank-id": "%d_%d" % (n,m)}, comment = "Add some extra metadata for the SVD")
 		ligolw_utils.write_filename(xmldoc, outfile, verbose = options.verbose)
+	split_bin_start += len(svd)
 
 	# some gymnastics to get the fiducial horizon template in the LR calculation
 	rows = metadata[svd[0]][clipleft:-clipright]