Try to avoid dotnet formating changes not in current commit

- formatted files are added into commits even when not intended

Author: dougbu

.githooks/pre-commit

@@ -1,8 +1,8 @@
 #!/bin/sh
 LC_ALL=C
 
-# Select files to format
-FILES=$(git show --name-only --pretty="")
+# Select files to format, ignoring broken, deleted, unmerged, and unknown files
+FILES=$(git show --diff-filter=bdux --name-only --pretty="")
 [ -z "$FILES" ] && exit 0
 
 # Format all selected files with dotnet-format
@@ -12,4 +12,4 @@ echo "dotnet-format: $(git diff --cached --numstat | wc -l) file(s) formatted."
 
 # Add files to staging
 echo "$FILES" | xargs git add
-exit 0
+exit 0