milestone 1 review: claims span the run, explain's chain is opt-in and its own, overrides keyed by clean path, splice and enum guards

1 files changed, 21 insertions, 12 deletions

diff --git a/internal/engine/session.go b/internal/engine/session.go
index 33b6a76..d79c364 100644
--- a/internal/engine/session.go
+++ b/internal/engine/session.go
@@ -25,6 +25,7 @@ type Session struct {
 	j      *journal.Writer
 	run    string
 	claims *plan.Claims
+	landed []string // where this run's applied files ended up, in order
 	dry    bool
 }
 
@@ -90,26 +91,34 @@ func (s *Session) Plan(ctx context.Context, d *Dir) (*DirPlan, error) {
 	return s.e.Plan(ctx, d, s.claims)
 }
 
-// Apply carries out the approved files of dp and logs the run's steps. A
-// real run applies each directory before the next is planned, so afterwards
-// the disk is the truth for the next one: only the paths this directory's
-// files ended up at stay claimed, which keeps a later (on-conflict
-// overwrite) from displacing this run's own result (spec §7.4). A dry
-// session keeps every claim, since it applies nothing.
+// Apply carries out the approved files of dp and logs the run's steps,
+// remembering where they ended up for FinishDirectory.
 func (s *Session) Apply(ctx context.Context, dp *DirPlan, approved map[string]bool) (*ApplyResult, error) {
 	if err := s.OpenLog(); err != nil {
 		return nil, err
 	}
 	res, err := s.e.Apply(ctx, dp, approved, s.j, s.run)
-	if !s.dry {
-		s.claims = plan.NewClaims()
-		for _, p := range landedAt(res) {
-			s.claims.Claim(p)
-		}
-	}
+	s.landed = append(s.landed, landedAt(res)...)
 	return res, err
 }
 
+// FinishDirectory ends one directory of a real run: the disk is now the
+// truth for the next one, so the claims start again from where this run's
+// files have actually ended up - every directory's, not just this one's
+// (spec §7.4, plan 13 review F3). A path this directory planned but did not
+// apply is free again; a path it did apply stays protected from a later
+// (on-conflict overwrite) for the rest of the run, even across a directory
+// that applies nothing. A dry run applies nothing and keeps every claim.
+func (s *Session) FinishDirectory() {
+	if s.dry {
+		return
+	}
+	s.claims = plan.NewClaims()
+	for _, p := range s.landed {
+		s.claims.Claim(p)
+	}
+}
+
 // landedAt is where res's files ended up: each copy, and the last place a
 // move or rename put a file - not a path it passed through and left, and
 // nothing at all for a file deleted for good.