Automate the preparation step for a new release

Summary: Added a script that prepares the repo for facebook's new rocksdb release, which will automatically do some necessary work to make sure this repo is ready for 3rdparty release.

Test Plan:
Run this script and observed:

* new version was created (both in local and remote repo) as a git tag.
* build_version.cc was updated
* build_detect_platform was changed so that it won't create any new change.

Reviewers: haobo, dhruba, sdong, igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15003

Author: Kai Liu

build_tools/make_new_version.sh

@@ -0,0 +1,61 @@
+#!/bin/bash
+#  Copyright (c) 2013, Facebook, Inc.  All rights reserved.
+#  This source code is licensed under the BSD-style license found in the
+#  LICENSE file in the root directory of this source tree. An additional grant
+#  of patent rights can be found in the PATENTS file in the same directory.
+
+set -e
+# Print out the colored progress info so that it can be brainlessly 
+# distinguished by users.
+function title() {
+  echo -e "\033[1;32m$*\033[0m"
+}
+
+usage="Create new rocksdb version and prepare it for the release process\n"
+usage+="USAGE: ./make_new_version.sh <version>"
+
+# -- Pre-check
+if [[ $# < 1 ]]; then
+  echo -e $usage
+  exit 1
+fi
+
+ROCKSDB_VERSION=$1
+
+GIT_BRANCH=`git rev-parse --abbrev-ref HEAD`
+if [ $GIT_BRANCH != "master" ]; then
+  echo "Error: Current branch is '$GIT_BRANCH', Please switch to master branch."
+fi
+
+# --Step 1: cutting new tag
+title "Adding new tag for this release ..."
+git tag -a "$ROCKSDB_VERSION.fb" -m "Rocksdb $ROCKSDB_VERSION"
+
+# Setting up the proxy for remote repo access
+export http_proxy=http://172.31.255.99:8080
+export https_proxy="$http_proxy";
+
+title "Pushing new tag to remote repo ..."
+proxycmd.sh git push origin --tags
+
+# --Step 2: Update README.fb
+title "Updating the latest version info in README.fb ..."
+sed -i "s/Latest release is [0-9]\+.[0-9]\+.fb/Latest release is $ROCKSDB_VERSION.fb/" README.fb
+git commit README.fb -m "update the latest version in README.fb to $ROCKSDB_VERSION"
+proxycmd.sh git push
+
+# --Step 3: Prepare this repo for 3rd release
+title "Cleaning up repo ..."
+make clean
+git clean -fxd
+
+title "Generating the build info ..."
+# Comment out the call of `build_detection_version` so that the SHA number and build date of this
+# release will remain constant. Otherwise everytime we run "make" util/build_version.cc will be 
+# overridden.
+sed -i 's/^\$PWD\/build_tools\/build_detect_version$//' build_tools/build_detect_platform
+
+# Generate util/build_version.cc
+build_tools/build_detect_version
+
+title "Done!"