Add and update documentation about return codes

2 files changed, 13 insertions, 1 deletions

diff --git a/README.rst b/README.rst
index ccc74d9..f67f72e 100644
--- a/README.rst
+++ b/README.rst
@@ -126,6 +126,17 @@ Options::
       -vv, --verbose        Print out file names while processing
 
 
+------------
+Return Codes
+------------
+
+Normally YAPF returns zero on successful program termination and non-zero otherwise.
+
+If ``--diff`` is supplied, YAPF returns zero when no changes were necessary, non-zero
+otherwise (including program error). You can use this in a CI workflow to test that code
+has been YAPF-formatted.
+
+
 Formatting style
 ================
 
diff --git a/yapf/__init__.py b/yapf/__init__.py
index 0322b31..6281f07 100644
--- a/yapf/__init__.py
+++ b/yapf/__init__.py
@@ -49,7 +49,8 @@ def main(argv):
       in argv[0]).
 
   Returns:
-    0 if there were no changes, non-zero otherwise.
+    Zero on successful program termination, non-zero otherwise.
+    With --diff: zero if there were no changes, non-zero otherwise.
 
   Raises:
     YapfError: if none of the supplied files were Python files.