Allow to copy untouched files rather than rewrite them

Practically we may often want to rewrite only those files affected by reduction and copy the untouched files verbatim to avoid the extensive cost of rewriting. This is particularly excessive as often aggregators with few INSTRUMENT sources will get rewritten while those with many CONTORL sources remain untouched.

This MR adds a flag --output-untouched-copy that allows to automatically make a verbatim copy of untouched aggregator files instead. It only works with --output-scope all --output-layout collection and is ignored otherwise with a warning.

FYI @jmalka

added 1 commit

• b0fecd28 - Add --output-untouched-copy parameter to copy rather than rewrite untouched files

Compare with previous version

Tested successfully in the preparations of reducing p2654. For r0172, the difference in runtime touching a single aggregator with aggressive reductions (i.e. little to be actually rewritten) is 1min with copy and 14min without.

mentioned in commit a872d46d

merged