test: cover -x cross-device skip without root; harden OneFileSystem tests

Add a rootless unit test that reaches the actual st_dev skip branch in both the sequential and parallel (-m) scanners: a symlink nested under the scan root points at a directory on /dev/shm (a different device than the build fs) and, under --copy-links semantics, -x must drop that subtree while a plain scan includes it. Skips only when no cross-device target exists. Integration OneFileSystem test now cleans both dest dirs up front and reports a busy test mountpoint instead of ignoring the umount result. RSYNC_COMPAT.md notes that cross-filesystem mount-point subdirectories are dropped entirely (rsync parity).
2026-09-06 12:49:26 +02:00
parent 2bcc20aa08
commit 2d841405e6
3 changed files with 159 additions and 2 deletions
@@ -64,7 +64,7 @@ This document maps rsync's full feature set to FastSync's current implementation
 | `--existing` | Skip creating new files on receiver | ✅ Implemented | Existing destination files continue through normal update handling |
 | `--ignore-existing` | Skip updating existing files | ❌ Not Implemented | |
 | `--remove-source-files` | Sender removes regular files after confirmed transfer | ✅ Implemented | |
-| `-x`, `--one-file-system` | Do not cross filesystem boundaries | ✅ Implemented | Sender scanner captures the root device and skips descending into mount-point crossings (`st_dev` differs) |
+| `-x`, `--one-file-system` | Do not cross filesystem boundaries | ✅ Implemented | Sender scanner captures the root device and skips descending into mount-point crossings (`st_dev` differs); cross-filesystem mount-point subdirectories are dropped entirely, matching rsync |
 | `-F` | Add the default `.rsync-filter` rules | ❌ Not Implemented | |

 ## 4. Directory Options