Allow overwriting output groups

@bertsky wrote in #245:

(The --force option is not exposed to those CLIs.)

I often have a usage pattern of 1. force-removing an output group to 2. run a processor again, e.g.:

ocrd workspace remove-group -rf OCR-D-IMG-BINPAGE
ocrd workspace remove-group -rf OCR-D-IMG-BIN
ocrd-olena-binarize -I OCR-D-IMG -O OCR-D-IMG-BINPAGE,OCR-D-IMG-BIN \
    -p "$ocrd_olena_binarize_parameters"

or

ocrd workspace remove-group -rf OCR-D-SEG-LINE
ocrd-sbb-textline-detector -I OCR-D-IMG-BINPAGE -O OCR-D-SEG-LINE \
    -p "$ocrd_sbb_textline_detector_parameters"

It would be great if the processor CLI wrapper would provide --force to reduce this to:

ocrd-olena-binarize --force -I OCR-D-IMG -O OCR-D-IMG-BINPAGE,OCR-D-IMG-BIN \
    -p "$ocrd_olena_binarize_parameters"

and

ocrd-sbb-textline-detector --force -I OCR-D-IMG-BINPAGE -O OCR-D-SEG-LINE \
    -p "$ocrd_sbb_textline_detector_parameters"

[kba]

–overwrite would overwrite the whole group if it exists (that is remove all files in the group for all pages, regardless of what pages the processor will process) –overwrite --page-id xyz would overwrite just the files for the specified page if they exist

Sounds good, I’ll go implement it this way.

first writing to a temporary output group, and if that worked without errors, replacing the output group with the new one

That would also be possible but could cause different problems with consistency and produce counterintuitive results (“I pressed Ctrl-C after 30 images but processor produced no results in the output-file-grp”).

[mikegerber]

And probably not call it --force but --overwrite because the latter is more specific.

Just ideas for the semantics:

• --overwrite would overwrite the whole group if it exists (that is remove all files in the group for all pages, regardless of what pages the processor will process)
• --overwrite --page-id xyz would overwrite just the files for the specified page if they exist

The first one is my use case, the latter might be useful for someone.