autoroller: Always roll and improve description

In order to minimize bisection ranges when the roll breaks, we want
to update the chromium_revision as often as possible.
Even if a roll doesn't bring in changed dependencies or Clang version,
it still brings in changes in the Chromium build toolchain.

The description now contains links to all dependencies that change
(if any).

BUG=webrtc:4688
R=phoglund@webrtc.org

Review URL: https://codereview.webrtc.org/1381963003 .

Cr-Commit-Position: refs/heads/master@{#10141}

1 files changed, 46 insertions, 27 deletions

diff --git a/tools/autoroller/roll_chromium_revision.py b/tools/autoroller/roll_chromium_revision.py
index 9752275913..4a52be06e9 100755
--- a/tools/autoroller/roll_chromium_revision.py
+++ b/tools/autoroller/roll_chromium_revision.py
@@ -22,6 +22,7 @@ import urllib
 
 CHROMIUM_SRC_URL = 'https://chromium.googlesource.com/chromium/src'
 CHROMIUM_COMMIT_TEMPLATE = CHROMIUM_SRC_URL + '/+/%s'
+CHROMIUM_LOG_TEMPLATE = CHROMIUM_SRC_URL + '/+log/%s'
 CHROMIUM_FILE_TEMPLATE = CHROMIUM_SRC_URL + '/+/%s/%s'
 
 COMMIT_POSITION_RE = re.compile('^Cr-Commit-Position: .*#([0-9]+).*$')
@@ -44,7 +45,8 @@ CLANG_UPDATE_SCRIPT_LOCAL_PATH = os.path.join('tools', 'clang', 'scripts',
                                               'update.sh')
 
 DepsEntry = collections.namedtuple('DepsEntry', 'path url revision')
-ChangedDep = collections.namedtuple('ChangedDep', 'path current_rev new_rev')
+ChangedDep = collections.namedtuple('ChangedDep',
+                                    'path url current_rev new_rev')
 
 
 def ParseDepsDict(deps_content):
@@ -219,9 +221,9 @@ def CalculateChangedDeps(current_deps, new_deps):
           'Should never find more than one entry matching %s in %s, found %d' %
           (entry.path, new_entries, len(new_matching_entries)))
       if not new_matching_entries:
-        result.append(ChangedDep(entry.path, entry.revision, 'None'))
+        result.append(ChangedDep(entry.path, entry.url, entry.revision, 'None'))
       elif entry != new_matching_entries[0]:
-        result.append(ChangedDep(entry.path, entry.revision,
+        result.append(ChangedDep(entry.path, entry.url, entry.revision,
                                  new_matching_entries[0].revision))
   return result
 
@@ -243,45 +245,51 @@ def CalculateChangedClang(new_cr_rev):
   new_clang_update_sh = ReadRemoteCrFile(CLANG_UPDATE_SCRIPT_URL_PATH,
                                          new_cr_rev).splitlines()
   new_rev = GetClangRev(new_clang_update_sh)
-  return ChangedDep(CLANG_UPDATE_SCRIPT_LOCAL_PATH, current_rev, new_rev)
+  return ChangedDep(CLANG_UPDATE_SCRIPT_LOCAL_PATH, None, current_rev, new_rev)
 
 
-def GenerateCommitMessage(current_cr_rev, new_cr_rev, changed_deps_list,
-                          clang_change):
+def GenerateCommitMessage(current_cr_rev, new_cr_rev, current_commit_pos,
+                          new_commit_pos, changed_deps_list, clang_change):
   current_cr_rev = current_cr_rev[0:7]
   new_cr_rev = new_cr_rev[0:7]
   rev_interval = '%s..%s' % (current_cr_rev, new_cr_rev)
+  git_number_interval = '%s:%s' % (current_commit_pos, new_commit_pos)
 
-  current_git_number = ParseCommitPosition(ReadRemoteCrCommit(current_cr_rev))
-  new_git_number = ParseCommitPosition(ReadRemoteCrCommit(new_cr_rev))
-  git_number_interval = '%s:%s' % (current_git_number, new_git_number)
-
-  commit_msg = ['Roll chromium_revision %s (%s)' % (rev_interval,
+  commit_msg = ['Roll chromium_revision %s (%s)\n' % (rev_interval,
                                                     git_number_interval)]
+  commit_msg.append('Change log: %s' % (CHROMIUM_LOG_TEMPLATE % rev_interval))
+  commit_msg.append('Full diff: %s\n' % (CHROMIUM_COMMIT_TEMPLATE %
+                                         rev_interval))
+
   # TBR field will be empty unless in some custom cases, where some engineers
   # are added.
   tbr_authors = ''
+
   if changed_deps_list:
-    commit_msg.append('\nRelevant changes:')
+    commit_msg.append('Changed dependencies:')
 
     for c in changed_deps_list:
-      commit_msg.append('* %s: %s..%s' % (c.path, c.current_rev[0:7],
-                                          c.new_rev[0:7]))
+      commit_msg.append('* %s: %s/+log/%s..%s' % (c.path, c.url,
+                                                  c.current_rev[0:7],
+                                                  c.new_rev[0:7]))
       if 'libvpx' in c.path:
         tbr_authors += 'marpan@webrtc.org, stefan@webrtc.org, '
 
     change_url = CHROMIUM_FILE_TEMPLATE % (rev_interval, 'DEPS')
-    commit_msg.append('Details: %s' % change_url)
+    commit_msg.append('DEPS diff: %s\n' % change_url)
+  else:
+    commit_msg.append('No dependencies changed.')
 
   if clang_change.current_rev != clang_change.new_rev:
-    commit_msg.append('\nClang version changed %s:%s' %
+    commit_msg.append('Clang version changed %s:%s' %
                       (clang_change.current_rev, clang_change.new_rev))
     change_url = CHROMIUM_FILE_TEMPLATE % (rev_interval,
                                            CLANG_UPDATE_SCRIPT_URL_PATH)
     commit_msg.append('Details: %s' % change_url)
     tbr_authors += 'pbos@webrtc.org'
   else:
-    commit_msg.append('\nClang version was not updated in this roll.')
+    commit_msg.append('No update to Clang.')
+
   commit_msg.append('\nTBR=%s\n' % tbr_authors)
   return '\n'.join(commit_msg)
 
@@ -362,6 +370,9 @@ def main():
                  help=('Calculate changes and modify DEPS, but don\'t create '
                        'any local branch, commit, upload CL or send any '
                        'tryjobs.'))
+  p.add_argument('--allow-reverse', action='store_true', default=False,
+                 help=('Allow rolling back in time (disabled by default but '
+                       'may be useful to be able do to manually).'))
   p.add_argument('-s', '--skip-try', action='store_true', default=False,
                  help='Do everything except sending tryjobs.')
   p.add_argument('-v', '--verbose', action='store_true', default=False,
@@ -382,32 +393,40 @@ def main():
 
   _EnsureUpdatedMasterBranch(opts.dry_run)
 
-  if not opts.revision:
+  new_cr_rev = opts.revision
+  if not new_cr_rev:
     stdout, _ = _RunCommand(['git', 'ls-remote', CHROMIUM_SRC_URL, 'HEAD'])
     head_rev = stdout.strip().split('\t')[0]
     logging.info('No revision specified. Using HEAD: %s', head_rev)
-    opts.revision = head_rev
+    new_cr_rev = head_rev
 
   deps_filename = os.path.join(CHECKOUT_ROOT_DIR, 'DEPS')
   local_deps = ParseLocalDepsFile(deps_filename)
   current_cr_rev = local_deps['vars']['chromium_revision']
 
+  current_commit_pos = ParseCommitPosition(ReadRemoteCrCommit(current_cr_rev))
+  new_commit_pos = ParseCommitPosition(ReadRemoteCrCommit(new_cr_rev))
+
   current_cr_deps = ParseRemoteCrDepsFile(current_cr_rev)
-  new_cr_deps = ParseRemoteCrDepsFile(opts.revision)
+  new_cr_deps = ParseRemoteCrDepsFile(new_cr_rev)
 
-  changed_deps = sorted(CalculateChangedDeps(current_cr_deps, new_cr_deps))
-  clang_change = CalculateChangedClang(opts.revision)
-  if changed_deps or clang_change:
-    commit_msg = GenerateCommitMessage(current_cr_rev, opts.revision,
+  if new_commit_pos > current_commit_pos or opts.allow_reverse:
+    changed_deps = sorted(CalculateChangedDeps(current_cr_deps, new_cr_deps))
+    clang_change = CalculateChangedClang(new_cr_rev)
+    commit_msg = GenerateCommitMessage(current_cr_rev, new_cr_rev,
+                                       current_commit_pos, new_commit_pos,
                                        changed_deps, clang_change)
     logging.debug('Commit message:\n%s', commit_msg)
   else:
-    logging.info('No deps changes detected when rolling from %s to %s. '
-                 'Aborting without action.', current_cr_rev, opts.revision)
+    logging.info('Currently pinned chromium_revision: %s (#%s) is newer than '
+                 '%s (#%s). To roll to older revisions, you must pass the '
+                 '--allow-reverse flag.\n'
+                 'Aborting without action.', current_cr_rev, current_commit_pos,
+                 new_cr_rev, new_commit_pos)
     return 0
 
   _CreateRollBranch(opts.dry_run)
-  UpdateDeps(deps_filename, current_cr_rev, opts.revision)
+  UpdateDeps(deps_filename, current_cr_rev, new_cr_rev)
   _LocalCommit(commit_msg, opts.dry_run)
   _UploadCL(opts.dry_run)
   _LaunchTrybots(opts.dry_run, opts.skip_try)