plan 9: overwrite never trashes a directory or another scanned file

1 files changed, 15 insertions, 0 deletions

diff --git a/internal/plan/conflict.go b/internal/plan/conflict.go
index 8747669..c4c6b64 100644
--- a/internal/plan/conflict.go
+++ b/internal/plan/conflict.go
@@ -15,6 +15,7 @@ import (
 // tests can supply a stub and Build stays pure otherwise.
 type Disk interface {
 	Exists(path string) bool
+	Regular(path string) bool
 	SameContent(a, b string) (bool, error)
 }
 
@@ -29,6 +30,13 @@ func (OS) Exists(path string) bool {
 	return err == nil
 }
 
+// Regular reports whether path is a regular file, not following a symlink
+// at path itself.
+func (OS) Regular(path string) bool {
+	fi, err := os.Lstat(path)
+	return err == nil && fi.Mode().IsRegular()
+}
+
 // SameContent delegates to internal/dup, the one place content identity is
 // decided.
 func (OS) SameContent(a, b string) (bool, error) {
@@ -40,6 +48,7 @@ func (OS) SameContent(a, b string) (bool, error) {
 type NoDisk struct{}
 
 func (NoDisk) Exists(string) bool                       { return false }
+func (NoDisk) Regular(string) bool                      { return false }
 func (NoDisk) SameContent(string, string) (bool, error) { return false, nil }
 
 // claimed is the set of destination paths already spoken for by an earlier
@@ -89,6 +98,12 @@ func resolveConflict(kind Kind, policy config.Conflict, src, dst string, d Disk,
 		return dst, "target exists", ""
 	case config.ConflictOverwrite:
 		if onDisk && !c[dst] {
+			// Only a regular file is ever trashed to make room (review M4):
+			// a directory or link of the same name stays, and so does the
+			// step - skipped, saying why.
+			if !d.Regular(dst) {
+				return dst, "target is not a regular file", ""
+			}
 			// The existing file is trashed first (plan 4). Only the first
 			// step to reach this path may displace it: once another step
 			// in this same plan has already claimed dst, that path will