1532413 - `moz-phab submit` does not correctly reset branch state on an error

Status: RESOLVED DUPLICATE of bug 1484838

(Conduit :: moz-phab, defect)

Description

[Nathan Froyd [:froydnj]]

I hit:

froydnj@hawkeye:~/src/gecko$ moz-phab submit cc9da25^ HEAD
Submitting 5 commits:
(New) 3eeb8e3344b5 Bug 1523996 - part 5 - bulk-read/write adjacent POD fields in IPDL-defined structs; r=Alex_Gaynor
(New) 8e713e66e3b0 Bug 1523996 - part 4 - add static assertions for member layout; r=Alex_Gaynor
(New) f37a5daa4ad0 Bug 1523996 - part 3 - factor out reading/writing sentinels; r=Alex_Gaynor
(New) 7de7b78ae5a0 Bug 1523996 - part 2 - pack IPDL-defined struct members better; r=Alex_Gaynor
(New) cc9da25e3b46 Bug 1523996 - part 1 - compute a packing permutation for structure fields; r=Alex_Gaynor
Submit to Phabricator (YES/No/Always)? YES

Creating new revision:
cc9da25e3b46 Bug 1523996 - part 1 - compute a packing permutation for structure fields; r=Alex_Gaynor
Linting...
No lint engine configured for this project.
Running unit tests...
No unit test engine is configured for this project.
 Exception 
ERR-CONDUIT-CORE: Local VCS (git) is different from the one defined in the repository (hg).
To use Phabricator with git-cinnabar please follow the docs at https://moz-conduit.readthedocs.io/en/latest/phabricator-user.html#using-git-cinnabar
(Run with `--trace` for a full exception trace.)
CalledProcessError: Command '['/home/froydnj/.mozbuild/arcanist/bin/arc', 'diff', '--base', 'arc:this', '--allow-untracked', '--no-amend', '--no-ansi', '--message-file', '/tmp/tmp6ewIDQ', '--create']' returned non-zero exit status 1

which is fine, because I had missed a setup step. What was not fine was the next thing that happened, after fixing my arcanist checkout:

froydnj@hawkeye:~/src/gecko$ moz-phab submit cc9da25^ HEAD
fatal: ref HEAD is not a symbolic ref
Git failed to read the branch name.
The repository is in a detached HEAD state.
You need to run the *git checkout <branch-name>* command.

Failures shouldn't leave the repository in a detached HEAD state.