···

       
20
       
20
       
 
       
  prepareIncrementalBuild = drv: drv.overrideAttrs (old: {

     

       
21
       
21
       
 
       
    outputs = [ "out" ];

     

       
22
       
22
       
 
       
    name = drv.name + "-incrementalBuildArtifacts";

     

       
23
       
23
       
+
       
    # To determine differences between the state of the build directory

     

       
24
       
24
       
+
       
    # from an earlier build and  a later one we store the state of the build

     

       
25
       
25
       
+
       
    # directory before build, but after patch phases.

     

       
26
       
26
       
+
       
    # This way, the same derivation can be used multiple times and only changes are detected.

     

       
27
       
27
       
+
       
    # Additionally Removed files are handled correctly in later builds.

     

       
23
       
28
       
 
       
    preBuild = (old.preBuild or "") + ''

     

       
24
       
29
       
 
       
      mkdir -p $out/sources

     

       
25
       
30
       
 
       
      cp -r ./* $out/sources/

     

       
26
       
31
       
 
       
    '';

     

       
27
       
32
       
 
       


     

       
33
       
33
       
+
       
    # After the build the build directory is copied again

     

       
34
       
34
       
+
       
    # to get the output files.

     

       
35
       
35
       
+
       
    # We copy the complete build folder, to take care for

     

       
36
       
36
       
+
       
    # Build tools, building in the source directory, instead of

     

       
37
       
37
       
+
       
    # having a build root directory, e.G the Linux kernel.

     

       
28
       
38
       
 
       
    installPhase = ''

     

       
29
       
39
       
 
       
      mkdir -p $out/outputs

     

       
30
       
40
       
 
       
      cp -r ./* $out/outputs/

     
···

       
40
       
50
       
 
       
    * in mkIncrementalBuild drv incrementalBuildArtifacts

     

       
41
       
51
       
 
       
  */

     

       
42
       
52
       
 
       
  mkIncrementalBuild = drv: previousBuildArtifacts: drv.overrideAttrs (old: {

     

       
53
       
53
       
+
       
    # The actual incremental build phase.

     

       
54
       
54
       
+
       
    # We compare the changed sources from a previous build with the current and create a patch

     

       
55
       
55
       
+
       
    # Afterwards we clean the build directory to copy the previous output files (Including the sources)

     

       
56
       
56
       
+
       
    # The source difference patch is applied to get the latest changes again to allow short build times.

     

       
43
       
57
       
 
       
    preBuild = (old.preBuild or "") + ''

     

       
44
       
58
       
 
       
      set +e

     

       
45
       
59
       
 
       
      diff -ur ${previousBuildArtifacts}/sources ./ > sourceDifference.patch