start adding build_plan to track the build process for a job

tools/src/build_plan.rs

@@ -0,0 +1,30 @@
+// This is a representation of the recipes/steps that result in a
+// desired Output.  It's a path from starting points/vitamins to the
+// desired Output.
+
+use crate::quantity::*;
+
+// FIXME: this isn't the correct abstraction for Item
+#[derive(Debug)]
+pub struct Item {
+    pub name: String,
+    pub quantity: Quantity,
+}
+
+#[derive(Debug)]
+pub struct BuildPlan<'a> {
+    // Keys are the names of Items.
+    // Values are Items, which are just the name and a Quantity.
+    pub bom: std::collections::HashMap<String, Item>,
+
+    pub repos: &'a crate::repos::Repos,
+}
+
+impl<'a> BuildPlan<'a> {
+    pub fn new(repos: &'a crate::repos::Repos) -> Self {
+        BuildPlan {
+            bom: std::collections::HashMap::<String, Item>::new(),
+            repos,
+        }
+    }
+}