metadata times: -U/--atimes, -N/--crtimes, --open-noatime, -O/-J

Capture+transmit source atime (pre-read stat; O_NOATIME sender guard) and birth
time (statx STATX_BTIME); receiver restores atime with mtime (crtime not settable
portably -> transmitted, explicitly not applied). --open-noatime is client-only.
-O/-J documented as accepted no-ops (FastSync never preserves dir/symlink times).
Wire: metadata frame gains atime/crtime val+sec+nsec; PROTOCOL_VERSION
2.11.0->2.12.0. Review fixes: gate atime capture to Linux (no epoch clobber on
non-Linux), close fd on fdopen failure, honest -O/-J status (Compat no-op).

src/client/client_cli.c

@@ -4,6 +4,7 @@
 #include "compression.h"
 #include "config.h"
 #include "delta.h"
+#include "file.h"
 #include "file_list.h"
 #include "filter.h"
 #include "identity.h"
@@ -533,6 +534,11 @@ static const OptionEntry OPTION_TABLE[] = {
     {"--cvs-exclude", "-C", OPT_FLAG, offsetof(Config, cvs_exclude)},
     {"-F", NULL, OPT_FLAG, offsetof(Config, per_dir_filter)},
     {"--numeric-ids", NULL, OPT_FLAG, offsetof(Config, numeric_ids)},
+    {"--atimes", "-U", OPT_FLAG, offsetof(Config, preserve_atimes)},
+    {"--crtimes", "-N", OPT_FLAG, offsetof(Config, preserve_crtimes)},
+    {"--omit-dir-times", "-O", OPT_FLAG, offsetof(Config, omit_dir_times)},
+    {"--omit-link-times", "-J", OPT_FLAG, offsetof(Config, omit_link_times)},
+    {"--open-noatime", NULL, OPT_FLAG, offsetof(Config, open_noatime)},
 };
 
 /* Only boolean options with no required argument are safe to negate. */
@@ -794,6 +800,14 @@ int parse_args(Config* config, int argc, char* argv[], int* positional_args,
          config. */
       if (entry->offset == offsetof(Config, delete_missing_args))
         config->ignore_missing_args = true;
+      /* -U/--atimes and -N/--crtimes carry their times inside the metadata
+         payload, which is only transmitted when use_metadata is set, so either
+         one implies metadata transmission.  This is FastSync's broad -M bundle
+         (mode/mtime travel too); it does NOT enable ownership application,
+         which stays opt-in via the identity flags. */
+      if (entry->offset == offsetof(Config, preserve_atimes) ||
+          entry->offset == offsetof(Config, preserve_crtimes))
+        config->use_metadata = true;
       continue;
     }
 
@@ -1339,6 +1353,10 @@ int main(int argc, char* argv[]) {
     goto cleanup;
   }
 
+  /* --open-noatime is a sender-side policy: install it for every source read
+     (scan + data path) without touching the receiver. */
+  file_set_open_noatime(config->open_noatime);
+
   /* Initialize TLS if needed */
   if (config->use_tls)
     tls_global_init();

src/client/client_send.c

@@ -82,6 +82,8 @@ static bool prepare_scanner(const Config* config, int num_threads, PreparedScann
 
   ScannerOptions* options = &out->options;
   options->use_metadata = config->use_metadata;
+  options->preserve_atimes = config->preserve_atimes;
+  options->preserve_crtimes = config->preserve_crtimes;
   options->chunk_size = config->chunk_size;
   options->exclude_patterns = config->exclude_patterns;
   options->exclude_count = config->exclude_count;

src/client/scanner.c

@@ -320,6 +320,8 @@ DirectoryScanner* directory_scanner_create_with_options(const char* root_directo
   scanner->current_dir = NULL;
   scanner->current_path = NULL;
   scanner->use_metadata = options->use_metadata;
+  scanner->preserve_atimes = options->preserve_atimes;
+  scanner->preserve_crtimes = options->preserve_crtimes;
   scanner->chunk_size = options->chunk_size > 0 ? options->chunk_size : DESIRED_CHUNK_SIZE;
   scanner->exclude_patterns = options->exclude_patterns;
   scanner->exclude_count = options->exclude_count;
@@ -564,7 +566,8 @@ static File* dirs_root_dir_file(DirectoryScanner* scanner) {
   }
   file->is_dir = true;
   if (scanner->use_metadata) {
-    file->metadata = file_metadata_create(&st);
+    file->metadata = file_metadata_create(scanner->root_path, &st, scanner->preserve_atimes,
+                                          scanner->preserve_crtimes);
     if (!file->metadata) {
       file_destroy(file);
       scanner->failed = true;
@@ -641,7 +644,8 @@ static File* dirs_file_for_entry(DirectoryScanner* scanner, const char* entry) {
     }
   }
   if (scanner->use_metadata) {
-    file->metadata = file_metadata_create(&effective);
+    file->metadata = file_metadata_create(file->path, &effective, scanner->preserve_atimes,
+                                          scanner->preserve_crtimes);
     if (!file->metadata) {
       file_destroy(file);
       scanner->failed = true;
@@ -893,7 +897,8 @@ Chunk* directory_scanner_next(DirectoryScanner* scanner) {
         rel_copy = NULL;
       }
       if (scanner->use_metadata)
-        file->metadata = file_metadata_create(&stats);
+        file->metadata = file_metadata_create(file->path, &stats, scanner->preserve_atimes,
+                                              scanner->preserve_crtimes);
       if (scanner->use_metadata && !file->metadata) {
         free(rel_copy);
         file_destroy(file);
@@ -1208,7 +1213,8 @@ static void scan_root_entry(const ScannerOptions* options, const FilterNode* roo
     rel = NULL;
   }
   if (options->use_metadata)
-    file->metadata = file_metadata_create(&st);
+    file->metadata =
+        file_metadata_create(file->path, &st, options->preserve_atimes, options->preserve_crtimes);
   if (options->use_metadata && !file->metadata) {
     free(rel);
     file_destroy(file);

src/client/scanner.h

@@ -14,6 +14,10 @@
 
 typedef struct {
   bool use_metadata;
+  /* Phase 4 metadata capture: -U/--atimes and -N/--crtimes tell the scanner to
+   * capture the source access / birth time into each entry's FileMetadata. */
+  bool preserve_atimes;
+  bool preserve_crtimes;
   unsigned long long chunk_size;
   char** exclude_patterns;
   int exclude_count;
@@ -75,6 +79,8 @@ typedef struct {
   DIR* current_dir;
   char* current_path;
   bool use_metadata;
+  bool preserve_atimes;
+  bool preserve_crtimes;
   unsigned long long chunk_size;
   char** exclude_patterns;
   int exclude_count;