Update base.theme.bash

[zou000]

Add missing SCM_BRANCH variable for p4

Description

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• If my change requires a change to the documentation, I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• If I have added a new file, I also added it to clean_files.txt and formatted it using lint_clean_files.sh.
• I have added tests to cover my changes, and all the new and existing tests pass.

[akinomyoga]

This change anticipates the case when SCM_BRANCH is globally set. Then, I believe SCM_BRANCH should also be cleared before lines 339-341, which append values to SCM_BRANCH.

[zou000]

This change anticipates the case when SCM_BRANCH is globally set. Then, I believe SCM_BRANCH should also be cleared before lines 339-341, which append values to SCM_BRANCH.

SCM_BRANCH was not set before coming in this branch. I moved it to scm_prompt_vars so it will be initialized for all scm.

[seefood]

sounds legit