container inspect: make Mounts order deterministic

[thaJeztah]

daemon: sortMounts: rewrite with slices package

daemon: sortMounts: remove return value

sortMounts sorts the input in-place; the return value was added as part of
its initial implementation in 81fa9fe (#13161), and
from the looks of it was just for convenience.

Remove the return value to make it clear it sorts in-place and to not give
the impression that it returns a clone.

daemon: make mount sorting deterministic

Use the mount destination as a tie-breaker when mounts have the same
depth. This preserves the existing parent-before-child ordering while
ensuring that the same set of mounts always produces the same order.

daemon: sortMounts: move to container.SortMounts

Move the utility to the container package, which is where the Mount
type is defined, and to allow re-use of the utility both inside the
container package and the daemon package.

daemon/container: GetMountPoints: sort mount-points

Container mount-points are stored in a map, so GetMountPoints could return
them in arbitrary order.

Sort the result using the common mount-path ordering to provide deterministic
container inspect output.

Before this patch, order of mounts would be randomized in container inspect;

docker inspect mycontainer | jq .[].Mounts.[].Destination
"/hello"
"/hello/world"

docker inspect mycontainer | jq .[].Mounts.[].Destination
"/hello/world"
"/hello"

Release notes (optional)

Fix inconsistent mount ordering in `docker inspect` output (`GET /containers/{id}/json`) and container listings (`docker ps`, `GET /containers/json`).

A picture of a cute animal (not mandatory but encouraged)

[Copilot]

Pull request overview

This PR refactors mount sorting into daemon/container and aims to make docker inspect mount output deterministic by sorting mounts (and mount-points derived from a map) in a consistent parent-before-child order.

Changes:

• Move mount sorting into daemon/container.SortMounts and switch callers to sort in-place.
• Add unit tests for mount ordering and stability with duplicate destinations.
• Sort Container.GetMountPoints() results to avoid nondeterministic map iteration order in inspect output.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
daemon/volumes.go	Removes the old local mount sorting implementation and related imports.
daemon/volumes_windows.go	Updates Windows mount setup to use the shared mount sorting helper (currently with a compile issue noted in comments).
daemon/volumes_unix.go	Switches Unix mount setup to container.SortMounts (in-place sort).
daemon/oci_linux.go	Switches OCI spec mount sorting to container.SortMounts.
daemon/container/mounts.go	Introduces shared mount path comparison and exported SortMounts (currently missing destination tie-breaker per comments).
daemon/container/mounts_test.go	Adds test coverage for depth ordering, same-depth determinism, and stability for duplicates.
daemon/container/container_unix.go	Sorts returned mount-points for deterministic inspect output (currently missing a required import per comments).

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.

[GordonTheTurtle]

Assessment: 🟢 APPROVE

Reviewed the mount-sorting refactor (sortMounts → container.SortMounts, plus deterministic tie-breaking and sorted GetMountPoints output for docker inspect).

The refactor is sound:

• All previous sortMounts call sites (daemon/oci_linux.go, daemon/volumes_unix.go, daemon/volumes_windows.go) were correctly updated to call container.SortMounts in-place; no stale references to the removed function remain, and volumes_windows.go correctly relies on the in-place mutation rather than the removed return value.
• GetMountPoints sorting operates on a locally-built slice, so no race condition is introduced.
• The new depth-then-lexicographic tie-break preserves the original parent-before-child ordering guarantee while making output deterministic.

No high or medium severity issues were found in this diff.

_{Non-blocking notes from automated analysis (low severity, informational only):}

1. daemon/container/mounts_test.go — test cases only cover POSIX-style destinations (/etc, /var, ...). Since compareMountPaths/SortMounts are shared by both container_unix.go and container_windows.go's GetMountPoints, consider adding a case (or Windows-specific test) covering backslash/drive-letter destinations to lock in cross-platform behavior.
2. daemon/container/mounts.go — compareMountPaths (line 13) computes depth via separator count after filepath.Clean; / (root) and top-level paths like /etc both count as depth 1, so root/top-level ordering currently relies solely on the lexicographic tie-break. Works today, but isn't covered by a dedicated test case, so a future change to the tie-break could silently regress it.
3. daemon/container/mounts.go — the tie-break (cmp.Compare(a, b), line 22) is byte-wise/case-sensitive, which may not match case-insensitive filesystem semantics on Windows. Not a functional bug (case-differing destinations at equal depth can't be parent/child of each other), just worth being aware of if visible ordering differences are ever reported.