diff --git a/Jenkins/BETA-apply-patch/Jenkinsfile b/Jenkins/BETA-apply-patch/Jenkinsfile
index e0010ff..c8bec71 100644
--- a/Jenkins/BETA-apply-patch/Jenkinsfile
+++ b/Jenkins/BETA-apply-patch/Jenkinsfile
@@ -1 +1,98 @@
-// Copyright 2019 Google LLC
//
// Licensed under the the Apache License v2.0 with LLVM Exceptions (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://llvm.org/LICENSE.txt
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

def success = true
def failure_message = ""

pipeline {
    agent { label 'linux' }
    parameters {
        string(name: 'DIFF_ID')
        string(name: 'PHID')
        string(name: 'REV_ID')
    }
    environment {
            CONDUIT_TOKEN = credentials('phabricator-conduit-token')
            PHABRICATOR_HOST = 'https://reviews.llvm.org'
            LLVM_DIR = "${WORKSPACE}/llvm-project"
            SCRIPT_DIR = "${WORKSPACE}/llvm-premerge-checks/scripts"
            RESULT_DIR = "${WORKSPACE}/results"
            PHAB_LOG = "${RESULT_DIR}/.phabricator-comment"
            MY_BUILD_ID = "${JOB_BASE_NAME}-${BUILD_NUMBER}"
            TARGET_DIR = "/mnt/nfs/results/${MY_BUILD_ID}"
            RESULT_URL = "http://results.llvm-merge-guard.org/${MY_BUILD_ID}"
    }
    options {
        timeout(time:10, unit:'MINUTES')
    }
    stages {
        stage("build info"){
            steps {
                echo "Building diff ${DIFF_ID} with PHID ${PHID} for Revision ${REV_ID}"
                script {
                    currentBuild.displayName += " D${REV_ID}"
                    currentBuild.description = "<a href='https://reviews.llvm.org/D${REV_ID}'>D${REV_ID}</a>"
                }
            }
        }
        stage("git checkout"){
            steps {
                dir("${LLVM_DIR}"){
                  git url: 'git@github.com:llvm-premerge-tests/llvm-project.git'
                }
                dir("llvm-premerge-checks")
                {
                    git url: 'https://github.com/google/llvm-premerge-checks.git'
                }
                sh """
                  rm -rf ${RESULT_DIR}
                  mkdir -p ${RESULT_DIR}
                  """
            }
        }
        stage('arc patch'){
            steps {
                dir("${LLVM_DIR}"){
                  sh """
                    ${SCRIPT_DIR}/phabtalk/apply_patch2.py ${DIFF_ID} \
                      --token ${CONDUIT_TOKEN} \
                      --url ${PHABRICATOR_HOST} \
                      --comment-file ${PHAB_LOG} \
                      --push-branch
                  """
                 }
            }
        }
    }
    post {
        always {
            dir("${RESULT_DIR}") {
                // copy console log to result folder
                sh "wget -qO console-log.txt http://jenkins-ui.jenkins.svc.cluster.local:8080/job/${JOB_BASE_NAME}/${BUILD_NUMBER}/consoleText"
                sh "mkdir ${TARGET_DIR}"
                sh "cp * ${TARGET_DIR}"
            }

            sh """${SCRIPT_DIR}/phabtalk/phabtalk.py "${PHID}" "${DIFF_ID}" \
                --workspace "${LLVM_DIR}" \
                --conduit-token "${CONDUIT_TOKEN}" \
                --host "${PHABRICATOR_HOST}/api/" \
                --buildresult ${currentBuild.result} \
                --results-dir "${TARGET_DIR}" \
                --results-url "${RESULT_URL}" \
                --failures "Applying patch failed" \
                --name "apply patch"
                """
        }
    }
}
\ No newline at end of file
+// Copyright 2019 Google LLC
+//
+// Licensed under the the Apache License v2.0 with LLVM Exceptions (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://llvm.org/LICENSE.txt
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+def success = true
+def failure_message = ""
+
+pipeline {
+    agent { label 'linux' }
+    parameters {
+        string(name: 'DIFF_ID')
+        string(name: 'PHID')
+        string(name: 'REV_ID')
+    }
+    environment {
+            CONDUIT_TOKEN = credentials('phabricator-conduit-token')
+            PHABRICATOR_HOST = 'https://reviews.llvm.org'
+            LLVM_DIR = "${WORKSPACE}/llvm-project"
+            SCRIPT_DIR = "${WORKSPACE}/llvm-premerge-checks/scripts"
+            RESULT_DIR = "${WORKSPACE}/results"
+            PHAB_LOG = "${RESULT_DIR}/.phabricator-comment"
+            MY_BUILD_ID = "${JOB_BASE_NAME}-${BUILD_NUMBER}"
+            TARGET_DIR = "/mnt/nfs/results/${MY_BUILD_ID}"
+            RESULT_URL = "http://results.llvm-merge-guard.org/${MY_BUILD_ID}"
+    }
+    options {
+        timeout(time:10, unit:'MINUTES')
+    }
+    stages {
+        stage("build info"){
+            steps {
+                echo "Building diff ${DIFF_ID} with PHID ${PHID} for Revision ${REV_ID}"
+                script {
+                    currentBuild.displayName += " D${REV_ID}"
+                    currentBuild.description = "<a href='https://reviews.llvm.org/D${REV_ID}'>D${REV_ID}</a>"
+                }
+            }
+        }
+        stage("git checkout"){
+            steps {
+                dir("${LLVM_DIR}"){
+                  git url: 'git@github.com:llvm-premerge-tests/llvm-project.git'
+                }
+                dir("llvm-premerge-checks")
+                {
+                    git url: 'https://github.com/google/llvm-premerge-checks.git'
+                }
+                sh """
+                  rm -rf ${RESULT_DIR}
+                  mkdir -p ${RESULT_DIR}
+                  """
+            }
+        }
+        stage('arc patch'){
+            steps {
+                dir("${LLVM_DIR}"){
+                  sh """
+                    ${SCRIPT_DIR}/phabtalk/apply_patch2.py ${DIFF_ID} \
+                      --token ${CONDUIT_TOKEN} \
+                      --url ${PHABRICATOR_HOST} \
+                      --push-branch
+                  """
+                 }
+            }
+        }
+    }
+    post {
+        always {
+            dir("${RESULT_DIR}") {
+                // copy console log to result folder
+                sh "wget -qO console-log.txt http://jenkins-ui.jenkins.svc.cluster.local:8080/job/${JOB_BASE_NAME}/${BUILD_NUMBER}/consoleText"
+                sh "mkdir ${TARGET_DIR}"
+                sh "cp * ${TARGET_DIR}"
+            }
+
+            sh """${SCRIPT_DIR}/phabtalk/phabtalk.py "${PHID}" "${DIFF_ID}" \
+                --workspace "${LLVM_DIR}" \
+                --conduit-token "${CONDUIT_TOKEN}" \
+                --host "${PHABRICATOR_HOST}/api/" \
+                --buildresult ${currentBuild.result} \
+                --results-dir "${TARGET_DIR}" \
+                --results-url "${RESULT_URL}" \
+                --failures "Applying patch failed" \
+                --name "apply patch"
+                """
+        }
+    }
+}
diff --git a/Jenkins/apply-patch/Jenkinsfile b/Jenkins/apply-patch/Jenkinsfile
index e0010ff..c8bec71 100644
--- a/Jenkins/apply-patch/Jenkinsfile
+++ b/Jenkins/apply-patch/Jenkinsfile
@@ -1 +1,98 @@
-// Copyright 2019 Google LLC
//
// Licensed under the the Apache License v2.0 with LLVM Exceptions (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://llvm.org/LICENSE.txt
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

def success = true
def failure_message = ""

pipeline {
    agent { label 'linux' }
    parameters {
        string(name: 'DIFF_ID')
        string(name: 'PHID')
        string(name: 'REV_ID')
    }
    environment {
            CONDUIT_TOKEN = credentials('phabricator-conduit-token')
            PHABRICATOR_HOST = 'https://reviews.llvm.org'
            LLVM_DIR = "${WORKSPACE}/llvm-project"
            SCRIPT_DIR = "${WORKSPACE}/llvm-premerge-checks/scripts"
            RESULT_DIR = "${WORKSPACE}/results"
            PHAB_LOG = "${RESULT_DIR}/.phabricator-comment"
            MY_BUILD_ID = "${JOB_BASE_NAME}-${BUILD_NUMBER}"
            TARGET_DIR = "/mnt/nfs/results/${MY_BUILD_ID}"
            RESULT_URL = "http://results.llvm-merge-guard.org/${MY_BUILD_ID}"
    }
    options {
        timeout(time:10, unit:'MINUTES')
    }
    stages {
        stage("build info"){
            steps {
                echo "Building diff ${DIFF_ID} with PHID ${PHID} for Revision ${REV_ID}"
                script {
                    currentBuild.displayName += " D${REV_ID}"
                    currentBuild.description = "<a href='https://reviews.llvm.org/D${REV_ID}'>D${REV_ID}</a>"
                }
            }
        }
        stage("git checkout"){
            steps {
                dir("${LLVM_DIR}"){
                  git url: 'git@github.com:llvm-premerge-tests/llvm-project.git'
                }
                dir("llvm-premerge-checks")
                {
                    git url: 'https://github.com/google/llvm-premerge-checks.git'
                }
                sh """
                  rm -rf ${RESULT_DIR}
                  mkdir -p ${RESULT_DIR}
                  """
            }
        }
        stage('arc patch'){
            steps {
                dir("${LLVM_DIR}"){
                  sh """
                    ${SCRIPT_DIR}/phabtalk/apply_patch2.py ${DIFF_ID} \
                      --token ${CONDUIT_TOKEN} \
                      --url ${PHABRICATOR_HOST} \
                      --comment-file ${PHAB_LOG} \
                      --push-branch
                  """
                 }
            }
        }
    }
    post {
        always {
            dir("${RESULT_DIR}") {
                // copy console log to result folder
                sh "wget -qO console-log.txt http://jenkins-ui.jenkins.svc.cluster.local:8080/job/${JOB_BASE_NAME}/${BUILD_NUMBER}/consoleText"
                sh "mkdir ${TARGET_DIR}"
                sh "cp * ${TARGET_DIR}"
            }

            sh """${SCRIPT_DIR}/phabtalk/phabtalk.py "${PHID}" "${DIFF_ID}" \
                --workspace "${LLVM_DIR}" \
                --conduit-token "${CONDUIT_TOKEN}" \
                --host "${PHABRICATOR_HOST}/api/" \
                --buildresult ${currentBuild.result} \
                --results-dir "${TARGET_DIR}" \
                --results-url "${RESULT_URL}" \
                --failures "Applying patch failed" \
                --name "apply patch"
                """
        }
    }
}
\ No newline at end of file
+// Copyright 2019 Google LLC
+//
+// Licensed under the the Apache License v2.0 with LLVM Exceptions (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://llvm.org/LICENSE.txt
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+def success = true
+def failure_message = ""
+
+pipeline {
+    agent { label 'linux' }
+    parameters {
+        string(name: 'DIFF_ID')
+        string(name: 'PHID')
+        string(name: 'REV_ID')
+    }
+    environment {
+            CONDUIT_TOKEN = credentials('phabricator-conduit-token')
+            PHABRICATOR_HOST = 'https://reviews.llvm.org'
+            LLVM_DIR = "${WORKSPACE}/llvm-project"
+            SCRIPT_DIR = "${WORKSPACE}/llvm-premerge-checks/scripts"
+            RESULT_DIR = "${WORKSPACE}/results"
+            PHAB_LOG = "${RESULT_DIR}/.phabricator-comment"
+            MY_BUILD_ID = "${JOB_BASE_NAME}-${BUILD_NUMBER}"
+            TARGET_DIR = "/mnt/nfs/results/${MY_BUILD_ID}"
+            RESULT_URL = "http://results.llvm-merge-guard.org/${MY_BUILD_ID}"
+    }
+    options {
+        timeout(time:10, unit:'MINUTES')
+    }
+    stages {
+        stage("build info"){
+            steps {
+                echo "Building diff ${DIFF_ID} with PHID ${PHID} for Revision ${REV_ID}"
+                script {
+                    currentBuild.displayName += " D${REV_ID}"
+                    currentBuild.description = "<a href='https://reviews.llvm.org/D${REV_ID}'>D${REV_ID}</a>"
+                }
+            }
+        }
+        stage("git checkout"){
+            steps {
+                dir("${LLVM_DIR}"){
+                  git url: 'git@github.com:llvm-premerge-tests/llvm-project.git'
+                }
+                dir("llvm-premerge-checks")
+                {
+                    git url: 'https://github.com/google/llvm-premerge-checks.git'
+                }
+                sh """
+                  rm -rf ${RESULT_DIR}
+                  mkdir -p ${RESULT_DIR}
+                  """
+            }
+        }
+        stage('arc patch'){
+            steps {
+                dir("${LLVM_DIR}"){
+                  sh """
+                    ${SCRIPT_DIR}/phabtalk/apply_patch2.py ${DIFF_ID} \
+                      --token ${CONDUIT_TOKEN} \
+                      --url ${PHABRICATOR_HOST} \
+                      --push-branch
+                  """
+                 }
+            }
+        }
+    }
+    post {
+        always {
+            dir("${RESULT_DIR}") {
+                // copy console log to result folder
+                sh "wget -qO console-log.txt http://jenkins-ui.jenkins.svc.cluster.local:8080/job/${JOB_BASE_NAME}/${BUILD_NUMBER}/consoleText"
+                sh "mkdir ${TARGET_DIR}"
+                sh "cp * ${TARGET_DIR}"
+            }
+
+            sh """${SCRIPT_DIR}/phabtalk/phabtalk.py "${PHID}" "${DIFF_ID}" \
+                --workspace "${LLVM_DIR}" \
+                --conduit-token "${CONDUIT_TOKEN}" \
+                --host "${PHABRICATOR_HOST}/api/" \
+                --buildresult ${currentBuild.result} \
+                --results-dir "${TARGET_DIR}" \
+                --results-url "${RESULT_URL}" \
+                --failures "Applying patch failed" \
+                --name "apply patch"
+                """
+        }
+    }
+}
diff --git a/scripts/buildkite/apply_patch.sh b/scripts/buildkite/apply_patch.sh
index 4a66224..2bf0685 100755
--- a/scripts/buildkite/apply_patch.sh
+++ b/scripts/buildkite/apply_patch.sh
@@ -22,7 +22,8 @@ scripts/phabtalk/apply_patch2.py $ph_buildable_diff \
   --path "${BUILDKITE_BUILD_PATH}"/llvm-project-fork \
   --token $CONDUIT_TOKEN \
   --url $PHABRICATOR_HOST \
-  --comment-file apply_patch.txt \
+  --log-level $LOG_LEVEL \
+  --commit $BASE_COMMIT \
   --push-branch
 
 EXIT_STATUS=$?
diff --git a/scripts/buildkite/create_branch_pipeline.py b/scripts/buildkite/create_branch_pipeline.py
index bd01dcd..d959463 100755
--- a/scripts/buildkite/create_branch_pipeline.py
+++ b/scripts/buildkite/create_branch_pipeline.py
@@ -19,6 +19,9 @@ import yaml
 if __name__ == '__main__':
     queue_prefix = os.getenv("ph_queue_prefix", "")
     diff_id = os.getenv("ph_buildable_diff")
+    log_level = os.getenv('ph_log_level', 'INFO')
+    base_commit = os.getenv('ph_base_commit', 'auto')
+    run_build = os.getenv('ph_skip_build') is None
     steps = []
     create_branch_step = {
         'label': 'create branch',
@@ -26,6 +29,10 @@ if __name__ == '__main__':
         'commands': ['scripts/buildkite/apply_patch.sh'],
         'agents': {'queue': f'{queue_prefix}linux'},
         'timeout_in_minutes': 20,
+        'env': {
+            'LOG_LEVEL': log_level,
+            'BASE_COMMIT': base_commit,
+        }
     }
     build_linux_step = {
         'trigger': 'premerge-checks',
@@ -41,5 +48,6 @@ if __name__ == '__main__':
         if e.startswith('ph_'):
             build_linux_step['build']['env'][e] = os.getenv(e)
     steps.append(create_branch_step)
-    steps.append(build_linux_step)
+    if run_build:
+        steps.append(build_linux_step)
     print(yaml.dump({'steps': steps}))
diff --git a/scripts/phabtalk/apply_patch2.py b/scripts/phabtalk/apply_patch2.py
index 0f5259d..eb19443 100755
--- a/scripts/phabtalk/apply_patch2.py
+++ b/scripts/phabtalk/apply_patch2.py
@@ -16,10 +16,12 @@
 import argparse
 import datetime
 import json
+import logging
 import os
 import re
 import socket
 import subprocess
+import sys
 import time
 from typing import List, Optional, Tuple
 
@@ -53,9 +55,8 @@ class ApplyPatch:
     https://github.com/llvm/llvm-project or given a path to clone into.
     """
 
-    def __init__(self, path: str, diff_id: int, comment_file_path: str, token: str, url: str, git_hash: str,
+    def __init__(self, path: str, diff_id: int, token: str, url: str, git_hash: str,
                  push_branch: bool = False):
-        self.comment_file_path = comment_file_path
         self.push_branch = push_branch  # type: bool
         self.conduit_token = token  # type: Optional[str]
         self.host = url  # type: Optional[str]
@@ -64,18 +65,17 @@ class ApplyPatch:
         if not self.host.endswith('/api/'):
             self.host += '/api/'
         self.phab = self._create_phab()
-        self.base_revision = git_hash  # type: Optional[str]
-        self.msg = []  # type: List[str]
+        self.base_revision = git_hash  # type: str
 
         if not os.path.isdir(path):
-            print(f'{path} does not exist, cloning repository')
+            logging.info(f'{path} does not exist, cloning repository')
             # TODO: progress of clonning
             self.repo = Repo.clone_from(FORK_REMOTE_URL, path)
         else:
-            print('repository exist, will reuse')
+            logging.info('repository exist, will reuse')
             self.repo = Repo(path)  # type: Repo
         os.chdir(path)
-        print('working dir', os.getcwd())
+        logging.info(f'working dir {os.getcwd()}')
 
     @property
     def branch_name(self):
@@ -86,7 +86,7 @@ class ApplyPatch:
         """Load arc configuration from file if not set."""
         if self.conduit_token is not None or self.host is not None:
             return
-        print('Loading configuration from ~/.arcrc file')
+        logging.info('Loading configuration from ~/.arcrc file')
         with open(os.path.expanduser('~/.arcrc'), 'r') as arcrc_file:
             arcrc = json.load(arcrc_file)
         # use the first host configured in the file
@@ -95,24 +95,27 @@ class ApplyPatch:
 
     def run(self):
         """try to apply the patch from phabricator
-        
-        Write to `self.comment_file` for showing error messages on Phabricator.
+
         """
 
         try:
             self._refresh_master()
             revision_id, dependencies, base_revision = self._get_dependencies(self.diff_id)
             dependencies.reverse()  # Arrange deps in chronological order.
+            if self.base_revision != 'auto':
+                logging.info('Using base revision provided by command line\n{} instead of resolved\n{}'.format(
+                    self.base_revision, base_revision))
+                base_revision = self.base_revision
             self._create_branch(base_revision)
-            print('git reset, git cleanup...')
+            logging.info('git reset, git cleanup...')
             self.repo.git.reset('--hard')
             self.repo.git.clean('-fdx')
-            print('Analyzing {}'.format(diff_to_str(revision_id)))
+            logging.info('Analyzing {}'.format(diff_to_str(revision_id)))
             if len(dependencies) > 0:
-                print('This diff depends on: {}'.format(diff_list_to_str(dependencies)))
+                logging.info('This diff depends on: {}'.format(diff_list_to_str(dependencies)))
                 missing, landed = self._get_missing_landed_dependencies(dependencies)
-                print('  Already landed: {}'.format(diff_list_to_str(landed)))
-                print('  Will be applied: {}'.format(diff_list_to_str(missing)))
+                logging.info('  Already landed: {}'.format(diff_list_to_str(landed)))
+                logging.info('  Will be applied: {}'.format(diff_list_to_str(missing)))
                 if missing:
                     for revision in missing:
                         self._apply_revision(revision)
@@ -120,15 +123,17 @@ class ApplyPatch:
                     self.repo.config_writer().set_value("user", "name", "myusername").release()
                     self.repo.config_writer().set_value("user", "email", "myemail@example.com").release()
                     self.repo.git.commit('-a', '-m', 'dependencies')
-                print('All depended diffs are applied')
+                logging.info('All depended diffs are applied')
+            logging.info('applying original diff')
             self._apply_diff(self.diff_id, revision_id)
             if self.push_branch:
                 self._commit_and_push()
             else:
                 self.repo.git.add('-u', '.')
-            print('done.')
-        finally:
-            self._write_error_message()
+            return 0
+        except Exception as e:
+            logging.error(f'exception: {e}')
+            return 1
 
     def _refresh_master(self):
         """Update local git repo and origin.
@@ -138,7 +143,7 @@ class ApplyPatch:
         if not self.push_branch:
             return
 
-        print('Syncing local, origin and upstream...')
+        logging.info('Syncing local, origin and upstream...')
         self.repo.git.fetch('--all')
         self.repo.git.checkout('master')
         self.repo.git.reset('--hard')
@@ -150,27 +155,24 @@ class ApplyPatch:
         self.repo.git.pull('upstream', 'master')
         try:
             self.repo.git.push('origin', 'master')
-            print('refresh of master branch completed')
+            logging.info('refresh of master branch completed')
         except GitCommandError as e:
-            print('Info: Could not push to origin master.')
+            logging.info('Info: Could not push to origin master.')
 
     def _create_branch(self, base_revision: Optional[str]):
         self.repo.git.fetch('--all')
         if self.branch_name in self.repo.heads:
             self.repo.delete_head('--force', self.branch_name)
-        if self.base_revision is not None:
-            print('Using base revision provided by command line\n{} instead of resolved\n{}'.format(
-                self.base_revision, base_revision))
-            base_revision = self.base_revision
         try:
-            commit = self.repo.commit()
+            commit = self.repo.commit(base_revision)
         except BadName:
-            print('Revision {} not found in upstream repository, using master instead.'.format(base_revision))
+            logging.info('Revision {} not found in upstream repository, using master instead.'.format(base_revision))
             commit = self.repo.heads['master']
+        logging.info(f'creating branch {self.branch_name} at {commit.hexsha}')
         new_branch = self.repo.create_head(self.branch_name, commit.hexsha)
         self.repo.head.reference = new_branch
         self.repo.head.reset(index=True, working_tree=True)
-        print('Base revision is {}'.format(self.repo.head.commit.hexsha))
+        logging.info('Base branch revision is {}'.format(self.repo.head.commit.hexsha))
 
     def _commit_and_push(self):
         """Commit the patch and push it to origin."""
@@ -181,7 +183,7 @@ class ApplyPatch:
         self.repo.index.commit(message='applying Diff {}'.format(
             self.diff_id))
         self.repo.git.push('--force', 'origin', self.branch_name)
-        print('Branch {} pushed to origin'.format(self.branch_name))
+        logging.info('Branch {} pushed to origin'.format(self.branch_name))
         pass
 
     def _create_phab(self):
@@ -211,10 +213,12 @@ class ApplyPatch:
         """Get all dependencies for the diff.
         They are listed in reverse chronological order - from most recent to least recent."""
 
-        print('Getting dependencies of {}'.format(diff_id))
+        logging.info('Getting dependencies of {}'.format(diff_id))
         diff = self._get_diff(diff_id)
+        logging.debug(f'diff object: {diff}')
         revision_id = int(diff.revisionID)
         revision = self._get_revision(revision_id)
+        logging.debug(f'revision object: {revision}')
         base_revision = diff['sourceControlBaseRevision']
         if base_revision is None or len(base_revision) == 0:
             base_revision = 'master'
@@ -231,9 +235,9 @@ class ApplyPatch:
 
     def _apply_diff(self, diff_id: int, revision_id: int):
         """Download and apply a diff to the local working copy."""
-        print('Applying diff {} for revision {}...'.format(diff_id, diff_to_str(revision_id)))
-        # TODO: print diff or URL to it
+        logging.info('Applying diff {} for revision {}...'.format(diff_id, diff_to_str(revision_id)))
         diff = try_call(lambda: self.phab.differential.getrawdiff(diffID=str(diff_id)).response)
+        logging.debug(f'diff {diff_id}:\n{diff}')
         proc = subprocess.run('git apply -', input=diff, shell=True, text=True,
                               stdout=subprocess.PIPE, stderr=subprocess.PIPE)
         if proc.returncode != 0:
@@ -244,20 +248,9 @@ class ApplyPatch:
         revision = self._get_revision(revision_id)
         # take the diff_id with the highest number, this should be latest one
         diff_id = max(revision['diffs'])
+        logging.info(f'picking diff from revision {revision_id}: {diff_id} from {revision["diffs"]}')
         self._apply_diff(diff_id, revision_id)
 
-    def _write_error_message(self):
-        """Write the log message to a file."""
-        if self.comment_file_path is None:
-            return
-
-        if len(self.msg) == 0:
-            return
-        print('writing error message to {}'.format(self.comment_file_path))
-        with open(self.comment_file_path, 'a') as comment_file:
-            text = '\n\n'.join(self.msg)
-            comment_file.write(text)
-
     def _get_landed_revisions(self):
         """Get list of landed revisions from current git branch."""
         diff_regex = re.compile(r'^Differential Revision: https://reviews\.llvm\.org/(.*)$', re.MULTILINE)
@@ -274,7 +267,8 @@ class ApplyPatch:
             if result is not None:
                 yield result.group(1)
         if earliest_commit is not None:
-            print('Earliest analyzed commit in history', earliest_commit.hexsha, earliest_commit.committed_datetime)
+            logging.info(f'Earliest analyzed commit in history {earliest_commit.hexsha}, '
+                         f'{earliest_commit.committed_datetime}')
         return
 
     def _get_missing_landed_dependencies(self, dependencies: List[int]) -> Tuple[List[int], List[int]]:
@@ -308,24 +302,24 @@ def try_call(call):
         except socket.timeout as e:
             c += 1
             if c > 5:
-                print('Connection to Pharicator failed, giving up: {}'.format(e))
+                logging.error('Connection to Pharicator failed, giving up: {}'.format(e))
                 raise
-            print('Connection to Pharicator failed, retrying: {}'.format(e))
+            logging.error('Connection to Pharicator failed, retrying: {}'.format(e))
             time.sleep(c * 10)
 
 
 if __name__ == "__main__":
     parser = argparse.ArgumentParser(description='Apply Phabricator patch to working directory.')
     parser.add_argument('diff_id', type=int)
-    # TODO: instead of --comment-file use stdout / stderr.
     parser.add_argument('--path', type=str, help='repository path', default=os.getcwd())
-    parser.add_argument('--comment-file', type=str, dest='comment_file_path', default=None)
     parser.add_argument('--token', type=str, default=None, help='Conduit API token')
     parser.add_argument('--url', type=str, default=None, help='Phabricator URL')
-    parser.add_argument('--commit', dest='commit', type=str, default=None,
-                        help='Use this commit as a base. By default tool tries to pick the base commit itself')
+    parser.add_argument('--commit', dest='commit', type=str, default='auto',
+                        help='Use this commit as a base. For "auto" tool tries to pick the base commit itself')
     parser.add_argument('--push-branch', action='store_true', dest='push_branch',
                         help='choose if branch shall be pushed to origin')
+    parser.add_argument('--log-level', type=str, default='INFO')
     args = parser.parse_args()
-    patcher = ApplyPatch(args.path, args.diff_id, args.comment_file_path, args.token, args.url, args.commit, args.push_branch)
-    patcher.run()
+    logging.basicConfig(level=args.log_level, format='%(levelname)-7s %(message)s')
+    patcher = ApplyPatch(args.path, args.diff_id, args.token, args.url, args.commit, args.push_branch)
+    sys.exit(patcher.run())