Merging upstream version 3.4.0.

Signed-off-by: Daniel Baumann <daniel@debian.org>

pre_commit/xargs.py

@@ -24,6 +24,14 @@ TRet = TypeVar('TRet')
 
 
 def cpu_count() -> int:
+    try:
+        # On systems that support it, this will return a more accurate count of
+        # usable CPUs for the current process, which will take into account
+        # cgroup limits
+        return len(os.sched_getaffinity(0))
+    except AttributeError:
+        pass
+
     try:
         return multiprocessing.cpu_count()
     except NotImplementedError:
@@ -170,7 +178,8 @@ def xargs(
         results = thread_map(run_cmd_partition, partitions)
 
         for proc_retcode, proc_out, _ in results:
-            retcode = max(retcode, proc_retcode)
+            if abs(proc_retcode) > abs(retcode):
+                retcode = proc_retcode
             stdout += proc_out
 
     return retcode, stdout