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checkpointedBuilds: add comments in the code

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This commit is contained in:
Martin Messer 2022-12-20 10:43:15 +01:00
parent c85d18ff91
commit ddfddf4b71
1 changed files with 14 additions and 0 deletions
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14
pkgs/build-support/build-incremental.nix
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@ -20,11 +20,21 @@ rec {
prepareIncrementalBuild = drv: drv.overrideAttrs (old: {
outputs = [ "out" ];
name = drv.name + "-incrementalBuildArtifacts";
# To determine differences between the state of the build directory
# from an earlier build and a later one we store the state of the build
# directory before build, but after patch phases.
# This way, the same derivation can be used multiple times and only changes are detected.
# Additionally Removed files are handled correctly in later builds.
preBuild = (old.preBuild or "") + ''
mkdir -p $out/sources
cp -r ./* $out/sources/
'';
# After the build the build directory is copied again
# to get the output files.
# We copy the complete build folder, to take care for
# Build tools, building in the source directory, instead of
# having a build root directory, e.G the Linux kernel.
installPhase = ''
mkdir -p $out/outputs
cp -r ./* $out/outputs/
@ -40,6 +50,10 @@ rec {
* in mkIncrementalBuild drv incrementalBuildArtifacts
*/
mkIncrementalBuild = drv: previousBuildArtifacts: drv.overrideAttrs (old: {
# The actual incremental build phase.
# We compare the changed sources from a previous build with the current and create a patch
# Afterwards we clean the build directory to copy the previous output files (Including the sources)
# The source difference patch is applied to get the latest changes again to allow short build times.
preBuild = (old.preBuild or "") + ''
set +e
diff -ur ${previousBuildArtifacts}/sources ./ > sourceDifference.patch