This PR upstreams dependency-management commands from Mathlib:
- `#import_path Foo` prints the transitive import chain that brings
`Foo` into scope
- `assert_not_exists Foo` errors if declaration `Foo` exists (for
dependency management)
- `assert_not_imported Module` warns if `Module` is transitively
imported
- `#check_assertions` verifies all pending assertions are eventually
satisfied
These commands help maintain the independence of different parts of a
library by catching unintended transitive dependencies early.
### Example usage
```lean
-- Find out how Nat got into scope
#import_path Nat
-- Declaration Nat is imported via
-- Init.Prelude,
-- which is imported by Init.Coe,
-- which is imported by Init.Notation,
-- ...
-- which is imported by this file.
-- Assert that a declaration should not be in scope yet
assert_not_exists SomeAdvancedType
-- Assert that a module should not be imported
assert_not_imported Some.Heavy.Module
-- Verify all assertions are eventually satisfied
#check_assertions
```
Addresses
https://lean-fro.zulipchat.com/#narrow/channel/398861-general/topic/path.20of.20an.20import🤖 Prepared with Claude Code
---------
Co-authored-by: Claude <noreply@anthropic.com>
