notes.md

root

• common
  • a
    • b
      • c
  • x
    • y (current directory)
      • z.nix "../../a/b/c"

Rename/Move allowed?

• root: Yes/Yes
• common: Yes/Yes
• a: No/No
• b: No/No
• c: No/No
• x: Yes/No
• y: Yes/No
• z.nix: Yes/No

An arbitrary relative reference has

• A common ancestor directory (common) that's safe to rename/move
• An upwards path (z.nix, y, x) that's only safe to rename
• A downwards path (a, b, c) that's neither safe to move nor rename

Function to determine this needs to:

• Set dir to the directory of the file with the reference
• Mark the file with the reference as unsafe to move
• Process each reference path component:
  • If it's a .. component
    • Mark dir as unsafe to move
    • Set dir to its parent
  • Otherwise:
    • Set dir to <dir>/<component>
    • Mark <dir> as unsafe to move and rename

When we try to move a path, it should either work, or give an error like this:

Cannot perform this move because it would break the reference "../../foo/bar" at ::

To do this, we need a function that takes a move operation and tells us whether it's valid, like

fn check_move(from: Path, to: Path) -> Result<[Reference], ()>
fn check_rename(path: Path) -> Result<[Reference], ()>
fn check_move(path: Path) -> Result<[Reference], ()>

check_move(./foo/bar, ./foo/baz) should do:

• Determine whether it's a rename or a move
  • Call check_rename(./foo/bar) if it's a rename
  • Call check_move(./foo/bar) if it's a move

check_{rename,move} can just check their respective trees

At the beginning, create an empty tree from all files in the given root directory. Rose tree

data Tree = Tree [Reference] (Map String Tree)