"Improve this doc" links are missing

[bart-vmware]

The docfx links for "Improve this doc" (pointing to a GitHub source) are missing.

I suspect because of such lines in the cibuild output:

#12 2.179 [24-03-01 09:07:08.212]Info:[BuildCore.Build Document.Load.ConceptualDocumentProcessor](articles/***-basics-in-7-minutes.md)For git repo </docs>, using commit id b00b166d5da2231dadab34f1c8a89d88ac8f1af3 as the branch name.

To fix this, the DOCFX_SOURCE_BRANCH_NAME environment variable needs to be set.

For example, in a GitHub Actions workflow step:

env:
  DOCFX_SOURCE_BRANCH_NAME: ${{ github.base_ref || github.ref_name }}

[bart-vmware]

The workflow step was updated in #315, but the "Improve this doc" links are still missing.