pre-commit: fail gracefully if fixing whitespace removes all changes

1 files changed, 12 insertions, 1 deletions

diff --git a/dev/tools/pre-commit b/dev/tools/pre-commit
index c5f6868d1..656455aee 100755
--- a/dev/tools/pre-commit
+++ b/dev/tools/pre-commit
@@ -36,12 +36,23 @@ then
 
     # reset work tree
     git diff-index -p --cached HEAD > "$fixed_index"
-    git apply -R "$fixed_index"
+    # If all changes were bad whitespace changes the patch is empty
+    # making git fail. Don't fail now: we fix the worktree first.
+    if [ -s "$fixed_index" ]
+    then
+        git apply -R "$fixed_index"
+    fi
 
     # Fix worktree
     git apply --whitespace=fix "$tree"
     git diff --name-only -z | xargs -0 dev/tools/check-eof-newline.sh --fix
 
+    if ! [ -s "$fixed_index" ]
+    then
+        1>&2 echo "No changes after fixing whitespace issues!"
+        exit 1
+    fi
+
     # Check that we did fix whitespace
     if ! git diff-index --check --cached HEAD;
     then