First steps on migrating to a new version of mongo.

We're going to write a helper binary for this in Go, because:

- The currently maintained driver package supports mongo versions back
  to 2.6 (what we're using), which is not true for most other languages.
- We already have go in our toolchain for boringssl's test suite.
- The build is unlikely to break due to bitrot re: Go's toolchain.
- The generated binary is static, so all else fails we can just bundle
  the executable, though I don't anticipate that.
- I will be much more productive than in something else.

make-bundle.sh

@@ -131,6 +131,9 @@ fi
 # Extract bin/mongo and bin/mongod from the old sandstorm bundle, and place them in bundle/.
 tar xf $OLD_BUNDLE_PATH --transform=s/^${OLD_BUNDLE_BASE}/bundle/ $OLD_MONGO_FILES
 
+# Copy in our helper to move over to newer versions of mongo:
+cp tmp/sandstorm-migrate-mongo bundle/bin/
+
 cp $(which zip unzip xz gpg) bundle/bin
 
 # 'node-fibers' depends on a package (detect-libc) that uses various heuristics

src/sandstorm-migrate-mongo/go.ekam-rule

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+
+top=$PWD
+module_dir="$(dirname $0)"
+
+echo findProvider special:ekam-interceptor
+read INTERCEPTOR
+
+if test "$INTERCEPTOR" = ""; then
+  echo "error:  couldn't find intercept.so." >&2
+  exit 1
+fi
+
+# The go toolchain itself is statically linked, so we can't just
+# run `go build` with the interceptor. But we can just use find.
+# Note: it would be tempting at this point to skip the interceptor
+# alltogether, but we want to also re-run if new sources files are
+# added, even if none of the old ones references them.
+LD_PRELOAD=$INTERCEPTOR find $module_dir -type f -name '*.go'
+LD_PRELOAD=$INTERCEPTOR find $module_dir -type f -name go.mod
+
+echo newOutput sandstorm-migrate-mongo
+read OUTPUT_DISK_PATH
+
+cd $module_dir
+go build -o $top/$OUTPUT_DISK_PATH

src/sandstorm-migrate-mongo/go.mod

@@ -0,0 +1,3 @@
+module github.com/sandstorm-io/sandstorm/src/sandstorm-migrate-mongo
+
+go 1.18

src/sandstorm-migrate-mongo/main.go

@@ -0,0 +1,7 @@
+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("Hello, World!")
+}