Add self-contained automated server upgrade package

lib/backup_set.py

@@ -13,6 +13,7 @@ from pathlib import Path, PurePosixPath
 import re
 import subprocess
 import sys
+import time
 import tarfile
 
 FORMAT = 2
@@ -201,9 +202,38 @@ def write_status(folder, operation, run_id, code):
         os.replace(str(path) + ".tmp", path)
 
 
+def wait_nextcloud(directory, timeout):
+    timeout = int(timeout)
+    if timeout < 1 or timeout > 3600:
+        raise ValueError("WRITER_DRAIN_TIMEOUT must be 1..3600 seconds")
+    expected = {os.path.realpath(directory + "/cron.php"), os.path.realpath(directory + "/occ")}
+    deadline = time.monotonic() + timeout
+    while True:
+        found = []
+        for process in Path("/proc").iterdir():
+            if not process.name.isdigit() or int(process.name) == os.getpid():
+                continue
+            try:
+                args = (process / "cmdline").read_bytes().split(b"\0")
+                cwd = os.readlink(process / "cwd")
+                # Exact script arguments only: do not match this helper's NC_DIR
+                # argument, unrelated files, or arbitrary shell command strings.
+                if any(arg and os.path.realpath(os.path.join(cwd, os.fsdecode(arg))) in expected for arg in args):
+                    found.append(process.name)
+            except (FileNotFoundError, ProcessLookupError):
+                continue
+        if not found:
+            return
+        if time.monotonic() >= deadline:
+            raise ValueError("Nextcloud writers still active (PIDs: " + ", ".join(found) + ")")
+        time.sleep(1)
+
+
 def main():
     op, *args = sys.argv[1:]
-    if op == "status":
+    if op == "wait-nextcloud":
+        wait_nextcloud(*args)
+    elif op == "status":
         write_status(*args)
     elif op == "crypt":
         crypt(*args)