Enum Durability 

#[non_exhaustive]
pub enum Durability {
    Durable,
    NotDurable,
    Unknown,
}

Whether a path string keeps pointing at the same (logical) target across rebuild / upgrade / reboot.

This is a durable-to-pin judgement: a Durable path may be baked into a launchd plist / systemd unit and is expected to survive upgrades and reboots. Judgement is per candidate — for the same binary, the reference path (/opt/homebrew/bin/git) can be Durable while its canonical realpath (/opt/homebrew/Cellar/git/2.44.0/bin/git) is NotDurable.

Judging model (allow-list)

1. NotDurable is decided first: versioned-install / ephemeral / build-output / project-local patterns.
2. Otherwise, if the path is under a known durable location (the “environment-wide reference surfaces”: standard system bins, profile bins matched by their exact structure, and shims at standard HOME-anchored locations), it is Durable.
3. Otherwise Unknown (treated as not-durable by Candidate::is_stable).

User dropbox directories (~/bin, ~/.local/bin) are deliberately not in the durable allow-list: they mix shebang-embedded scripts and versioned symlinks, so they fall through to Unknown.

Known limitations

Judgement is path-string based and cannot detect:

• shebang-embedded versioned dependencies: e.g. a script in a standard reference surface whose shebang points at a versioned interpreter (cpython@<ver>). Such a path may be judged Durable yet break on upgrade. This is why shebang-prone user dropboxes are excluded from the allow-list (see above), but the case cannot be ruled out entirely.
• environment-dependent paths: e.g. ~/.nix-profile is alive in some environments and dead in others; durability cannot be confirmed without inspecting the realpath.
• non-UTF-8 paths: pattern matching goes through Path::to_string_lossy, so a path containing non-UTF-8 bytes in a matched segment may compare unexpectedly; such paths typically fall through to Unknown (safe side).

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Durable

The path string keeps pointing at the same entity (or same logical target) across rebuild / upgrade / reboot.

NotDurable

Versioned-install / ephemeral / build-output / project-local etc.; baking this path into a service definition can break it.

Unknown

Matched neither a known durable nor a known not-durable pattern; cannot decide (safe side = treated as not-durable).

Trait Implementations

impl Clone for Durability

fn clone(&self) -> Durability

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Durability

impl Debug for Durability

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for Durability

impl PartialEq for Durability

fn eq(&self, other: &Durability) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for Durability