Makefile: Have patches reverted if they fail to apply cleanly #1952
Description
Heads currently applies patches that sometimes create files into build dir.
Heads buildsystem Makefile logic implies in build dir of modules/* :
- .canary : if doesn't exist, unpack tarball/clone repo and touch file
- .patched : if doesn't exist: apply patches/MODULE-VERSION.patch or patches/MODULE-VERSION/NUMBER-DESCRIPTION.patch application and touch file
- .configured: if doesn't exist, configure and touch
- .build: if doesn't exist, build and touch file
A proper rebuild helper would be to wipe .canary files. Doing so would force archive/git repo recreation, but issue arises when previously created files from patches are present in build dir.
Logic to cleanly attempt to apply patch, and if patch apply fails, revert patches in reverse order and then reapply patches would permit fast rebuilds of just changed source files per modules makefiles.
Unfortunately, this is way more work then expected under #1943 and was removed from there to this separate issue.
Original discussion:
How about
git apply -R? If heads build system could loop through patches and revert them, then maybe it would be fine? But you would have to revert them in reversed order, as opposed to the order they were applied...
Originally posted by @miczyg1 in #1943 (comment)