[clang] [clang-format] Add "three dot" diff option to git-clang-format (PR #74230)

[via cfe-commits]

================
@@ -153,7 +157,10 @@ def main():
   else:
     if len(commits) > 2:
       die('at most two commits allowed; %d given' % len(commits))
-  changed_lines = compute_diff_and_extract_lines(commits, files, opts.staged)
+  changed_lines = compute_diff_and_extract_lines(commits,
----------------
cor3ntin wrote:

Maybe we can add a `die` when diff_from_common_commit is true and len(commits) is < 2

https://github.com/llvm/llvm-project/pull/74230