docs(install): the path bug is symlinks, not /var

The comments and Agent Note blamed macOS resolving /var through
private/var. That is only how the mismatch surfaced in temp fixtures, since
mktemp hands back a /var path there.

The real condition is broader: Git always reports resolved paths, so
comparing one against an unresolved path disagrees whenever a symlink sits
anywhere above the checkout. A symlinked home directory alone triggers it —
reproduced with no /var involved — which is common wherever homes live
behind a symlink or on a network mount.

Naming the cause correctly keeps a reader from dismissing resolve_dir as
macOS-only defensiveness.
This commit is contained in:
Turtle
2026-07-31 23:47:58 +08:00
parent db432c1e74
commit c435350561
5 changed files with 11 additions and 9 deletions
@@ -20,7 +20,7 @@ The installer records nothing about where that repository lives. A container who
Adoption branches from `HEAD`, so committed work is what runs and uncommitted changes stay in the checkout. This is not prompted or warned about: the installer builds the layout and gets out of the way. Setting `DSH_SOURCE` to a different directory remains the one documented way to opt back into cloning a separate tree.
Every path comparison runs on physical paths through a `resolve_dir` helper, and every compared value is resolved at assignment rather than at the comparison. macOS resolves `/var` through a symlink to `/private/var`, so comparing a git-reported path against an unresolved one misclassified an existing managed install as a foreign clone and would have built a second container beside the real one. The same defect recurred twice more during review, both times as one side of a comparison left unresolved: a curl install's `REPO_ROOT`, and the container path it was compared against. `resolve_dir` therefore echoes a missing path back rather than failing, so a not-yet-created container needs no per-call fallback and no site can compare against an empty path by forgetting one; callers that need "does not exist" test the directory explicitly. `git rev-parse --path-format=absolute` would do the same job but requires git 2.31+.
Every path comparison runs on physical paths through a `resolve_dir` helper, and every compared value is resolved at assignment rather than at the comparison. Git always reports resolved paths, so comparing one against an unresolved path disagrees whenever a symlink sits anywhere above the checkout — a symlinked home directory is enough, and macOS reaches every `mktemp` path that way through `/var` -> `private/var`. The mismatch misclassified an existing managed install as a foreign clone and would have built a second container beside the real one. The same defect recurred twice more during review, both times as one side of a comparison left unresolved: a curl install's `REPO_ROOT`, and the container path it was compared against. `resolve_dir` therefore echoes a missing path back rather than failing, so a not-yet-created container needs no per-call fallback and no site can compare against an empty path by forgetting one; callers that need "does not exist" test the directory explicitly. `git rev-parse --path-format=absolute` would do the same job but requires git 2.31+.
Before `current` is repointed, the installer rejects a staging path that resolves to the repository itself, enforcing the upgrade contract that the launcher never resolves to the master clone.