Exploration of .NET build cache reuse bug (#9)

* add initial exploration of build cache reuse bug

discussed in paketo-buildpacks/dotnet-publish#279

* Add manual steps to dotnet cache reuse

* make a fresh copy of the app before rebuilding

Co-authored-by: Sophie Wigmore <[email protected]>

dotnet-build-cache-reuse/.gitignore

@@ -0,0 +1 @@
+dotnet-build-cache

dotnet-build-cache-reuse/README.md

@@ -0,0 +1,31 @@
+# Build cache issue reproduction
+
+## Testing locally
+
+Run
+```
+APP_SOURCE=<path to console app> go run main.go
+```
+
+## Testing in a docker container
+Use the official .NET SDK docker container for .NET 3.1 on top of ubuntu 18.04:
+1. Compile the go program for linux: `GOOS=linux go build .`
+3. Run the test in a container:
+  ```
+docker run -it -v $(pwd):/test \
+               -v $APP_SOURCE:/source \
+               --env APP_SOURCE=/source \
+               mcr.microsoft.com/dotnet/sdk:3.1-bionic \
+               /test/dotnet-build-cache
+  ```
+
+## Testing `dotnet publish` behaviour manually (on Linux)
+On Linux, it appears that the issue only occurs when orchestrated through
+Golang. When run manually or through a bash script, the failure does not crop
+up.
+
+Running the following appears to have the expected effects, in which the app
+serves the updated content:
+```
+./manual.sh --dir <path to some temporary directory"
+```

dotnet-build-cache-reuse/go.mod

@@ -0,0 +1,16 @@
+module github.com/fg-j/explorations/dotnet-build-cache
+
+go 1.18
+
+require (
+	github.com/paketo-buildpacks/occam v0.8.0
+	github.com/paketo-buildpacks/packit/v2 v2.3.0
+)
+
+require (
+	github.com/ForestEckhardt/freezer v0.0.11 // indirect
+	github.com/gabriel-vasile/mimetype v1.4.0 // indirect
+	github.com/oklog/ulid v1.3.1 // indirect
+	github.com/ulikunitz/xz v0.5.10 // indirect
+	golang.org/x/net v0.0.0-20220225172249-27dd8689420f // indirect
+)