utils/release: Add merge-git.sh
utils/release: Add merge-git.sh

Summary:
This script allows you to use git to backport a commit to a stable
branch while generating the exact same commit message (ignoring
whitespace) that you would get from using the merge.sh script with svn.

Reviewers: hansw

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D47760

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@334568 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm