Get the main branch of a Git repository

main-branch.sh

# From https://stackoverflow.com/questions/55266918/how-to-get-main-git-branch-name-from-command-line
# Original author: tukusejssirs (StackOverflow)

# Current local branch name
git rev-parse --abbrev-ref HEAD
# Output: branch

# Remote branch name that is tracked by current local branch
git for-each-ref --format='%(upstream:short)' $(git symbolic-ref -q HEAD)
# Output: origin/branch

# Local main branch name
git branch -vv | grep -Po \
  "^[\s\*]*\K[^\s]*(?=.*$(git branch -r | grep -Po "HEAD -> \K.*$").*)"
# Output: master

# Remote branch name that is tracked by local main branch
git branch -r | grep -Po "HEAD -> \K.*$"
# Output: origin/master