Cannot handle local branch being named differently from its remote branch

[stuartchaney]

Description

1. Team Member creates a PR on a branch named feature/replace-iphone-image-template

2. When checking out this PR on Atom. A branch is created named
   pr-81/stuartchaney/feature/replace-iphone-image-template

The branch created on my local system should be feature/replace-iphone-image-template

When clicking fetch from Atom this will lead to the following

Expected behavior:

local branch created from checking out PR should be feature/replace-iphone-image-template

Actual behavior:

local branch created from checking out PR is pr-81/stuartchaney/feature/replace-iphone-image-template

Reproduces how often:
100%

Versions

1.30.0

[rsese]

Thanks for the report! I can reproduce the error when trying to fetch/pull after checking out a pull request with 1.32.0-nightly11 on macOS 10.12.6.

[vanessayuenn]

The underlying issue is that we're not properly handling the case where the local branch is named differently from its upstream. Related issue: #918.