Change how commit messages are taken + multiple commits handling Multiple commits are separated and format-checked separately. Commit message is now taken solely from input_api. Tags paragraph now covers the very last paragraph until the first line that doesn't have a ":" Bug: angleproject:4662 Change-Id: I84fe3fd1ffc30f6892a5c9dbe545acf24b0fc595 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2241617 Commit-Queue: Manh Nguyen <nguyenmh@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>