arc diff --trace

 ARGV  '/usr/share/arcanist/bin/../scripts/arcanist.php' 'diff' '--trace'
 LOAD  Loaded "phutil" from "/usr/share/libphutil/src".
 LOAD  Loaded "arcanist" from "/usr/share/arcanist/src".
Config: Reading user configuration file "/home/theloudspeaker/.arcrc"...
Config: Did not find system configuration at "/etc/arcconfig".
Working Copy: Unable to find .arcconfig in any of these locations: /home/theloudspeaker/Style/lubuntu-default-settings/.arcconfig.
Working Copy: Path "/home/theloudspeaker/Style/lubuntu-default-settings" is part of `git` working copy "/home/theloudspeaker/Style/lubuntu-default-settings".
Working Copy: Project root is at "/home/theloudspeaker/Style/lubuntu-default-settings".
Config: Did not find local configuration at "/home/theloudspeaker/Style/lubuntu-default-settings/.git/arc/config".
>>> [0] (+0) <http> https://phab.lubuntu.me/api/user.whoami
<<< [0] (+1,556) <http> 1,556,143 us
>>> [1] (+1,560) <exec> $ git --version
<<< [1] (+1,564) <exec> 4,214 us
>>> [2] (+1,565) <exec> $ git status --porcelain=2 -z
<<< [2] (+1,571) <exec> 5,980 us
>>> [3] (+1,571) <exec> $ git rev-parse --verify HEAD^
<<< [3] (+1,576) <exec> 5,429 us
>>> [4] (+1,577) <exec> $ git rev-parse --abbrev-ref --symbolic-full-name '@{upstream}'
<<< [4] (+1,582) <exec> 5,497 us
>>> [5] (+1,583) <exec> $ git rev-parse --git-dir
<<< [5] (+1,588) <exec> 5,560 us
 Select a Default Commit Range

You're running a command which operates on a range of revisions (usually,
from some revision to HEAD) but have not specified the revision that should
determine the start of the range.

Previously, arc assumed you meant 'HEAD^' when you did not specify a start
revision, but this behavior does not make much sense in most workflows
outside of Facebook's historic git-svn workflow.

arc no longer assumes 'HEAD^'. You must specify a relative commit explicitly
when you invoke a command (e.g., `arc diff HEAD^`, not just `arc diff`) or
select a default for this working copy.

In most cases, the best default is 'origin/master'. You can also select
'HEAD^' to preserve the old behavior, or some other remote or branch. But you
almost certainly want to select 'origin/master'.

(Technically: the merge-base of the selected revision and HEAD is used to
determine the start of the commit range.)

    What default do you want to use? [origin/master]
>>> [6] (+3,198) <exec> $ git cat-file -t 'origin/master'
<<< [6] (+3,207) <exec> 8,193 us

[2019-04-10 21:37:50] EXCEPTION: (CommandException) Command failed with error #128!
COMMAND
git cat-file -t 'origin/master'

STDOUT
(empty)

STDERR
fatal: Not a valid object name origin/master
 at [<phutil>/src/future/exec/ExecFuture.php:380]
arcanist(), phutil()
  #0 ExecFuture::resolvex() called at [<arcanist>/src/repository/api/ArcanistRepositoryAPI.php:406]
  #1 ArcanistRepositoryAPI::execxLocal(string, string) called at [<arcanist>/src/repository/api/ArcanistGitAPI.php:365]
  #2 ArcanistGitAPI::buildBaseCommit(NULL) called at [<arcanist>/src/repository/api/ArcanistRepositoryAPI.php:599]
  #3 ArcanistRepositoryAPI::getBaseCommit() called at [<arcanist>/src/repository/api/ArcanistGitAPI.php:107]
  #4 ArcanistGitAPI::getLocalCommitInformation() called at [<arcanist>/src/workflow/ArcanistWorkflow.php:1081]
  #5 ArcanistWorkflow::calculateShouldAmend() called at [<arcanist>/src/workflow/ArcanistWorkflow.php:1069]
  #6 ArcanistWorkflow::getShouldAmend() called at [<arcanist>/src/workflow/ArcanistWorkflow.php:977]
  #7 ArcanistWorkflow::requireCleanWorkingCopy() called at [<arcanist>/src/workflow/ArcanistDiffWorkflow.php:691]
  #8 ArcanistDiffWorkflow::runDiffSetupBasics() called at [<arcanist>/src/workflow/ArcanistDiffWorkflow.php:467]
  #9 ArcanistDiffWorkflow::run() called at [<arcanist>/scripts/arcanist.php:394]