MB-22602: Add gerrit_move_to_kv_engine.py

Add a script to assist in migrating patches from the old memcached &
ep-engine repos to kv_engine.

The script will checkout the given change from Gerrit (memcached or
ep-engine), rebase into kv-engine, and then re-upload to Gerrit as a
new change against kv-engine.

The script automatically handles any rebases onto kv_engine which
don't otherwise conflict with upstream changes on the original repo -
i.e. if your patch would have rebased cleanly prior to the repo merge,
it should cleanly rebase onto the merged repo.

Example usage:

    scripts/gerrit_move_to_kv_engine.py drigby 78323

Example output:

    ** Migrating change 78323 - 'Move Blob to its own file (blob.{cc.h})' to kv_engine
    >> Fetching refs/changes/23/78323/3
    From http://review.couchbase.org/ep-engine
     * branch            refs/changes/23/78323/3 -> FETCH_HEAD
    -- Checking out change
    Previous HEAD position was bd68264... MB-22602: Add 'ep' as a subdir to engines/
    HEAD is now at 5b9d5a4... Move Blob to its own file (blob.{cc.h})
    -- Checking out latest kv_engine/master
    From github.com:couchbase/kv_engine
     * branch            master     -> FETCH_HEAD
    -- Rebasing change onto kv_engine/master
    << Uploading to Gerrit under kv_engine
    ** Successfully moved change to kv_engine

Change-Id: Ib84265529b2d4834d361c1b2db694fb73e9ab65a
Reviewed-on: http://review.couchbase.org/78522
Tested-by: Build Bot <build@couchbase.com>
Reviewed-by: Daniel Owen <owend@couchbase.com>

scripts/gerrit_move_to_kv_engine.py

@@ -0,0 +1,99 @@
+#!/usr/bin/env python2.7
+
+# Script to migrate a Gerrit Change from memcached or ep-engine repos
+# to the new kv_enigne repo.
+
+from __future__ import print_function
+import json
+import subprocess
+import sys
+import urllib2
+
+
+class bcolors:
+    HEADER = '\033[35m'
+    OKBLUE = '\033[34m'
+    OKGREEN = '\033[32m'
+    WARNING = '\033[33m'
+    FAIL = '\033[31m'
+    ENDC = '\033[0m'
+    BOLD = '\033[1m'
+    UNDERLINE = '\033[4m'
+
+
+def header(*args):
+    print(bcolors.OKBLUE, end='')
+    print(*args, end='')
+    print(bcolors.ENDC)
+
+
+def success(*args):
+    print(bcolors.OKGREEN, end='')
+    print(*args, end='')
+    print(bcolors.ENDC)
+
+
+if len(sys.argv) != 3:
+    print("""Migrates existing Gerrit changes from
+memcached/ep-engine repo to kv_engine repo.
+Checks out the specifed change, rebases to kv_engine and re-uploads to
+gerrit as a kv_engine change.
+
+Usage: gerrit_move_to_kv_engine.py <username> <change> <patch_set>
+
+    username   Username for Gerrit - see
+               http://review.couchbase.org/#/settings/ under 'Profile'
+    change     Change number
+
+Example: gerrit_move_to_kv_engine.py drigby memcached 78322 3
+    """, file=sys.stderr)
+    exit(1)
+
+user = sys.argv[1]
+change = sys.argv[2]
+
+info = dict()
+# Check this patch exists and determine which project it is from.
+try:
+    url = "http://review.couchbase.org/changes/{}".format(change)
+    f = urllib2.urlopen(url + "?o=CURRENT_REVISION&o=DOWNLOAD_COMMANDS")
+    data = f.read()[5:]  # The first 4 chars of response are ')]}'
+    info = json.loads(data)
+except urllib2.HTTPError as e:
+    print ("Error: failed to lookup change {} from {}: {}".format(change,
+                                                                  url, e),
+           file=sys.stderr)
+    print ("Check your Change is valid", file=sys.stderr)
+    exit(1)
+
+header("** Migrating change {} - '{}' to kv_engine".format(change,
+                                                           info['subject']))
+
+cur_rev_info = info['revisions'][info['current_revision']]
+fetch_info = cur_rev_info['fetch']['anonymous http']
+
+header(">> Fetching", fetch_info['ref'])
+subprocess.check_output(["git", "fetch", fetch_info['url'],
+                         fetch_info['ref']])
+
+header("-- Checking out change", bcolors.ENDC)
+subprocess.check_output(["git", "checkout", "FETCH_HEAD"])
+
+download_URL = "git@github.com:couchbase/kv_engine.git"
+header("-- Checking out latest kv_engine/master")
+subprocess.check_output(["git", "fetch", download_URL, "master"])
+
+header("-- Rebasing change onto kv_engine/master")
+if info['project'] == 'ep-engine':
+    subprocess.check_output(["git", "rebase",
+                             "--strategy=subtree",
+                             "--strategy-option=subtree=engines/ep",
+                             "FETCH_HEAD"])
+else:
+    subprocess.check_output(["git", "rebase", "FETCH_HEAD"])
+
+upload_URL = "ssh://{}@review.couchbase.org:29418/kv_engine".format(user)
+header("<< Uploading to Gerrit under kv_engine")
+subprocess.check_output(["git", "push", upload_URL,
+                         "HEAD:refs/for/master"])
+success("** Successfully moved change to kv_engine")