Remove ability to override temporary (working) folder

Little point to this feature - on most platforms the environment
variable can be overridden if desired to set a new root location.

At the same time, this change removes the ability to resume a partially
executed pipeline by deleting all of the results on failure.  If -k is
provided then the temporary files will survive but there's no way to
resume from them.  Because resuming doesn't really work away and would
only be useful to users experiencing very specific problems, this is
probably not worth it, so no major loss.  The intent of -k is to assist
debugging.

src/ocrmypdf.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 
 from contextlib import suppress
-from tempfile import NamedTemporaryFile
+from tempfile import NamedTemporaryFile, mkdtemp
 import sys
 import os
 import fileinput
@@ -9,10 +9,10 @@ import re
 import shutil
 import warnings
 import multiprocessing
+import atexit
 
 import PyPDF2 as pypdf
 from PIL import Image
-from parse import parse
 
 from subprocess import Popen, check_call, PIPE, CalledProcessError, \
     TimeoutExpired
@@ -23,7 +23,7 @@ except ImportError:
 
 
 from ruffus import transform, suffix, merge, active_if, regex, jobs_limit, \
-    mkdir, formatter, follows, subdivide, collate, check_if_uptodate
+    formatter, follows, subdivide, collate, check_if_uptodate
 import ruffus.cmdline as cmdline
 
 from .hocrtransform import HocrTransform
@@ -113,9 +113,6 @@ advanced = parser.add_argument_group(
 advanced.add_argument(
     '--deskew-provider', choices=['imagemagick', 'leptonica'],
     default='leptonica')
-advanced.add_argument(
-    '--temp-folder', default='', type=str,
-    help="folder where the temporary files should be placed")
 advanced.add_argument(
     '--tesseract-config', default=[], type=list, action='append',
     help="Tesseract configuration")
@@ -247,16 +244,24 @@ manager = multiprocessing.Manager()
 _pdfinfo = manager.list()
 _pdfinfo_lock = manager.Lock()
 
-if options.temp_folder == '':
-    options.temp_folder = 'tmp'
+work_folder = mkdtemp(prefix="com.github.ocrmypdf.")
+
+
+@atexit.register
+def cleanup_working_files(*args):
+    if options.keep_temporary_files:
+        print("Temporary working files saved at:")
+        print(work_folder)
+    else:
+        with suppress(FileNotFoundError):
+            shutil.rmtree(work_folder)
 
 
-@follows(mkdir(options.temp_folder))
 @transform(
     input=options.input_file,
     filter=suffix('.pdf'),
     output='.repaired.pdf',
-    output_dir=options.temp_folder,
+    output_dir=work_folder,
     extras=[_log, _pdfinfo, _pdfinfo_lock])
 def repair_pdf(
         input_file,
@@ -350,7 +355,7 @@ def get_pageinfo(input_file, pdfinfo, pdfinfo_lock):
     input=split_pages,
     filter=suffix('.page.pdf'),
     output='.page.png',
-    output_dir=options.temp_folder,
+    output_dir=work_folder,
     extras=[_log, _pdfinfo, _pdfinfo_lock])
 def rasterize_with_ghostscript(
         input_file,
@@ -506,7 +511,7 @@ def ocr_tesseract(
 @collate(
     input=[rasterize_with_ghostscript, preprocess_deskew, preprocess_clean],
     filter=regex(r".*/(\d{6})(?:\.page|\.pp-deskew|\.pp-clean)\.png"),
-    output=os.path.join(options.temp_folder, r'\1.image'),
+    output=os.path.join(work_folder, r'\1.image'),
     extras=[_log, _pdfinfo, _pdfinfo_lock])
 def select_image_for_pdf(
         infiles,
@@ -533,7 +538,7 @@ def select_image_for_pdf(
 @collate(
     input=[select_image_for_pdf, ocr_tesseract],
     filter=regex(r".*/(\d{6})(?:\.image|\.hocr)"),
-    output=os.path.join(options.temp_folder, r'\1.rendered.pdf'),
+    output=os.path.join(work_folder, r'\1.rendered.pdf'),
     extras=[_log, _pdfinfo, _pdfinfo_lock])
 def render_page(
         infiles,
@@ -556,7 +561,7 @@ def render_page(
     input=repair_pdf,
     filter=suffix('.repaired.pdf'),
     output='.pdfa_def.ps',
-    output_dir=options.temp_folder,
+    output_dir=work_folder,
     extras=[_log])
 def generate_postscript_stub(
         input_file,
@@ -567,7 +572,7 @@ def generate_postscript_stub(
 
 @merge(
     input=[render_page, generate_postscript_stub],
-    output=os.path.join(options.temp_folder, 'merged.pdf'),
+    output=os.path.join(work_folder, 'merged.pdf'),
     extras=[_log, _pdfinfo, _pdfinfo_lock])
 def merge_pages(
         input_files,
@@ -674,7 +679,7 @@ def validate_pdfa(
 
 # @active_if(ocr_required and options.exact_image)
 # @merge([render_hocr_blank_page, extract_single_page],
-#        os.path.join(options.temp_folder, "%04i.merged.pdf") % pageno)
+#        os.path.join(work_folder, "%04i.merged.pdf") % pageno)
 # def merge_hocr_with_original_page(infiles, output_file):
 #     with open(infiles[0], 'rb') as hocr_input, \
 #             open(infiles[1], 'rb') as page_input, \