modernisation of shell.call with shell.new,async_call
commit 5bcf4180
recipe: merge some functions in universal handling
The contents and effects of the functions were identical
commit c99c5204
recipe: only allow concurrent extract for tarballs
Extracting git repos concurrently can result in locking files being hit
commit 9bad1bfa
source: remove unused LocalTarball source class
commit e3f52096
replace some usage of shell.call with shell.async_call
commit 8bfb0f4a
replace some usage of shell.call with shell.new_call