docs: mark --compare-dest/--copy-dest/--link-dest implemented

Document receiver-side basis semantics, relative-to-destination-root confinement, content-verified matching, hard-link vs copy vs compare-only behavior, cross-filesystem copy fallback, repetition/priority, --delete exclusion, the implied --incremental and -s incompatibility, and each exact divergence from rsync (no dest deletion on compare-dest stale entries, no attribute re-application on basis hits, no re-linking of already-up-to-date dest files, sources matched from basis dirs kept under --remove-source-files).
2026-09-06 18:47:41 +02:00
parent 0d18b7fc87
commit 196a27689f
1 changed files with 3 additions and 3 deletions
@@ -171,9 +171,9 @@ This document maps rsync's full feature set to FastSync's current implementation
 |------|-------------------|-----------------|-------|
 | `--checksum` | Skip based on checksum | ✅ Implemented | With `--incremental`, compares xxHash64 content checksums; `-c` remains compression |
 | `--checksum-choice=STR` | Choose checksum algorithm | ❌ Not Implemented | xxHash used internally |
-| `--compare-dest=DIR` | Compare dest files relative to DIR | ❌ Not Implemented | Removed because it had no effect |
-| `--copy-dest=DIR` | Include copies of unchanged files | ❌ Not Implemented | Removed because it had no effect |
-| `--link-dest=DIR` | Hardlink to files when unchanged | ❌ Not Implemented | Removed because it had no effect |
+| `--compare-dest=DIR` | Compare dest files relative to DIR | ✅ Implemented | DIR is a receiver-side basis relative to the destination root (confined below it; absolute/`..` rejected). On the receiver's per-file check (implies `--incremental`) an exact match = same size + mtime (unless `--size-only`/`-I`) **and** equal xxHash64 of the sender's file; a match suppresses the data transfer. compare-dest never copies: it only skips a file the destination does **not** already hold (sparse destination, rsync parity), and is consulted before the normal delta/full paths. Repeatable; searched in command-line order, first match wins. Divergences: when the destination already holds a *different* version rsync deletes it but FastSync instead transfers the data (keeps the mirror complete; never deletes without `--delete`); attribute-only differences on a match are not re-applied (data is skipped so the sender never sends metadata); content is verified by xxHash64, stricter than rsync's default quick check. Requires `--incremental` (implied); needs the per-file check so it is incompatible with `-s` chunk serialization. Wire: new config fields (protocol bumped to 2.8.0) |
+| `--copy-dest=DIR` | Include copies of unchanged files | ✅ Implemented | Same basis rules as `--compare-dest`, but an exact match materializes a **local copy** of the DIR file into the destination (via the normal atomic temp+rename store path, so `--existing`/`--ignore-existing`/`--update`/`--backup`/`--delay-updates` all still apply) instead of transferring data. Repeatable; command-line order = priority. Content is xxHash64-verified before the copy. Divergences: attributes come from the basis file (sender metadata is not sent on a match); a match that differs only in attributes is copied with the basis attributes rather than rsync's "copy + fix attributes". Requires `--incremental` (implied); incompatible with `-s`. Wire: protocol 2.8.0 |
+| `--link-dest=DIR` | Hardlink to files when unchanged | ✅ Implemented | Same basis rules as `--copy-dest`, but an exact match installs an atomic **hard link** to the DIR file (temp hard link + rename) so no data or disk space is used; where the link is impossible (basis on another filesystem, filesystem refuses links) it falls back cleanly to a byte-identical local copy, never a corrupt/partial file. `--delay-updates` stages the link and publishes by rename, so the final entry stays a real hard link. Repeatable (searched in command-line order, first match wins). Content is xxHash64-verified before linking. Divergences: an already up-to-date destination file is not re-linked to a basis file (only files that would otherwise be written are linked); attributes on a link are the basis inode's own (metadata is never written through the shared inode, which would mutate the basis file); basis dirs are excluded from `--delete`; a `--remove-source-files` source matched from a basis dir is retained (treated as skipped). Requires `--incremental` (implied); incompatible with `-s`. Wire: protocol 2.8.0 |
 | `--fuzzy`, `--no-fuzzy` | Find similar file for basis | ❌ Not Implemented | |

 ## 12. Compression