1 files changed, 32 insertions, 0 deletions
diff --git a/pre_commit_hooks/util.py b/pre_commit_hooks/util.py
new file mode 100644
index 0000000..d6c90ae
--- /dev/null
+++ b/pre_commit_hooks/util.py
@@ -0,0 +1,32 @@
+from __future__ import annotations
+
+import subprocess
+from typing import Any
+
+
+class CalledProcessError(RuntimeError):
+    pass
+
+
+def added_files() -> set[str]:
+    cmd = ('git', 'diff', '--staged', '--name-only', '--diff-filter=A')
+    return set(cmd_output(*cmd).splitlines())
+
+
+def cmd_output(*cmd: str, retcode: int | None = 0, **kwargs: Any) -> str:
+    kwargs.setdefault('stdout', subprocess.PIPE)
+    kwargs.setdefault('stderr', subprocess.PIPE)
+    proc = subprocess.Popen(cmd, **kwargs)
+    stdout, stderr = proc.communicate()
+    stdout = stdout.decode()
+    if retcode is not None and proc.returncode != retcode:
+        raise CalledProcessError(cmd, retcode, proc.returncode, stdout, stderr)
+    return stdout
+
+
+def zsplit(s: str) -> list[str]:
+    s = s.strip('\0')
+    if s:
+        return s.split('\0')
+    else:
+        return []