eval: execute "$ exec expressions" in the directory of the current tree

Teach from_path() to use the parent directory of the specified
path as the config root. This allows us to write tests to ensure
that "$ <command>" exec expressions are executed with the
current directory set to the directory of the tree.

Signed-off-by: David Aguilar <davvid@gmail.com>

src/eval.rs

@@ -215,7 +215,6 @@ pub fn tree_value(
     })
     .to_string();
 
-    // TODO exec_expression_with_path() to use the tree path.
     // NOTE: an environment must not be calculated here otherwise any
     // exec expression will implicitly depend on the entire environment,
     // and potentially many variables (including itself).  Exec expressions

src/model.rs

@@ -1250,7 +1250,11 @@ impl ApplicationContext {
 
     /// Construct an ApplicationContext from a path using default MainOptions.
     pub fn from_path(pathbuf: std::path::PathBuf) -> Result<Self, errors::GardenError> {
-        Self::from_path_and_root(pathbuf, None)
+        if let Some(root_dir) = pathbuf.parent().map(std::path::Path::to_owned) {
+            Self::from_path_and_root(pathbuf, Some(&root_dir))
+        } else {
+            Self::from_path_and_root(pathbuf, None)
+        }
     }
 
     /// Construct an ApplicationContext from a path using default MainOptions.

src/query.rs

@@ -317,7 +317,6 @@ pub fn tree_context(
     garden: Option<&str>,
 ) -> Result<model::TreeContext, errors::GardenError> {
     let mut ctx = model::TreeContext::new("", config.get_id(), None, None);
-    // TODO: grafted trees
     if let Some(context) = tree_from_name(config, tree, None, None) {
         ctx.tree = context.tree;
     } else {

tests/data/garden.yaml

@@ -92,6 +92,8 @@ trees:
     url: https://example.com/replacement/tree
     replace: true
 
+  trees/prebuilt: "file://${repos}/example.git"
+
 templates:
   echo-template-extended:
     extend: echo-template

tests/data/trees/prebuilt/README.md

@@ -0,0 +1,4 @@
+# Test tree data
+
+This directory is used by the tests to simulate the existence of the
+`example/tree`, which is referenced by `tests/data/graden.yaml`.

tests/eval_test.rs

@@ -112,6 +112,18 @@ fn exec_expression() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn exec_expression_in_tree_context() -> Result<()> {
+    let app_context =
+        garden::model::ApplicationContext::from_path_string("tests/data/garden.yaml")?;
+    let config = app_context.get_root_config();
+    let context = garden::query::tree_context(&config, "trees/prebuilt", None)?;
+    let value = garden::eval::tree_value(&app_context, &config, "$ pwd", &context.tree, None);
+    assert!(value.ends_with("/trees/prebuilt"));
+
+    Ok(())
+}
+
 /// Ensure that shell $variables can be used.
 #[test]
 fn shell_variable_syntax() -> Result<()> {