conda: avoid py3.x-conda cross-contamination

[dannf]

Anything in the top-level directory of this package will end up getting installed into each version of the python module. We already use the prevent-inclusion parameter to prevent those files from being copied in. Now that we're using "cleanup" as a holding area, we need to include that as well.

This was causing the usr/bin/* files from all previously built modules to be included in subsequent ones:

  # apk info -L py3.12-conda | grep cleanup
  WARNING: opening /work/packages: No such file or directory
  usr/lib/python3.12/site-packages/cleanup/3.10/bin/conda
  usr/lib/python3.12/site-packages/cleanup/3.11/bin/conda
  usr/lib/python3.12/site-packages/melange-out/py3.11-conda/usr/lib/python3.11/site-packages/cleanup/3.10/bin/conda

And, because melange adds dependencies for paths in the shebangs, we were getting dependencies on additional python versions.

[murraybd]

Could we not modify py/pip-build-install rather than potentially modifying multiple packages in the same way?

[dannf]

I had considered it a feature that this pipeline failed when given bogus input because, in most cases, it seems like an absent path would be due to a mistake. What if instead we detect this case and emit a warning? Something like this not-yet-tested change:

diff --git a/pipelines/py/pip-build-install.yaml b/pipelines/py/pip-build-install.yaml
index 8cfa9d5a5..6b6a4bf01 100644
--- a/pipelines/py/pip-build-install.yaml
+++ b/pipelines/py/pip-build-install.yaml
@@ -92,13 +92,23 @@ pipeline:
         fi
       fi
 
+      add_prevent() {
+        if [ -e "$1" ]; then
+          ( vr tar -Apf "$2" && vr rm -rf "$1" ) ||
+             { echo "ERROR: failed adding $1 to prevent-inclusion.tar"; exit 1; }
+          echo "prevented-inclusion of $1"
+          return
+        fi
+        echo "WARNING: prevents-inclusion path $1 not found, ignoring."
+      }
+
+      pitar="$tmpd/prevent-inclusion.tar"
       prevents="${{inputs.prevent-inclusion}}"
       if [ -n "$prevents" ]; then
+         # initialize empty tar file
+         tar -cf "$pitar" -T /dev/null
          # do not allow expansion of prevents
-         ( set -f; vr tar -cpf "$tmpd/prevent-inclusion.tar" $prevents &&
-           vr rm -rf $prevents ) ||
-           { echo "ERROR: failed creation of prevent-inclusion.tar with $prevents"; exit 1; }
-         echo "prevented-inclusion of $prevents"
+         ( set -f; for p in $prevents; do add_prevent "$p" "$pitar"; done )
       fi
 
       [ -d build ] && hadbuild=true || hadbuild=false