parent branch / base branch

Unfortunately, it is not possible to find the name of the parent/base branch.

Git stores commits and pointers, not branch ancestry.

That means:

• a branch is just a movable name that points to one commit
• Git knows commit parents, but not "this branch was created from that branch"
• after more commits, rebases, merges, or deleted branches, that information is gone

But Git cannot reliably tell you:

• "feature-2 was created from feature-1"

If you are not asking Git about branch ancestry, but the hosting platform about the current PR, then CLI tools can help:

• GitHub: gh pr view --json baseRefName --jq .baseRefName
• GitLab: glab mr view --output json | jq -r .target_branch - Codeberg: berg --output json --non-interactive pull list --state open | jq -r --arg branch "$(git branch --show-current)" '[.[] | select(.head.ref == $branch)][0].base.ref'