datastore: add max-depth to recursive namespace iter

on depth == 0 we only yield the anchor ns, this simplifies usage in
the API as for, e.g. list-snapthos the depth == 0 means only the
snapshots from the passed namespace, nothing below.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

pbs-datastore/examples/ls-snapshots.rs

@@ -7,12 +7,20 @@ use pbs_datastore::DataStore;
 fn run() -> Result<(), Error> {
     let base: PathBuf = match std::env::args().skip(1).next() {
         Some(path) => path.into(),
-        None => bail!("no path passed"),
+        None => bail!("no path passed!\n\nusage: ls-snapshots <path> [<max-depth>]"),
+    };
+    let max_depth: Option<usize> = match std::env::args().skip(2).next() {
+        Some(depth) => match depth.parse::<usize>() {
+            Ok(depth) if depth < 8 => Some(depth),
+            Ok(_) => bail!("max-depth must be < 8"),
+            Err(err) => bail!("couldn't parse max-depth from {depth} - {err}"),
+        },
+        None => None,
     };
 
     let store = unsafe { DataStore::open_path("", &base, None)? };
 
-    for ns in store.recursive_iter_backup_ns_ok(Default::default())? {
+    for ns in store.recursive_iter_backup_ns_ok(Default::default(), max_depth)? {
         println!("found namespace store:/{}", ns);
 
         for group in store.iter_backup_groups(ns)? {