@netlify/config/lib/options/branch.js

Netlify config module

import { execaCommand } from 'execa';
// Find out git branch among (in priority order):
//   - `branch` option
//   - `BRANCH` environment variable
//   - `HEAD` branch (using `git`)
//   - `main` (using `git`)
//   - 'master' (fallback)
export const getBranch = async function ({ branch, repositoryRoot }) {
    if (branch) {
        return branch;
    }
    const headBranch = await getGitBranch(repositoryRoot, 'HEAD');
    if (headBranch !== undefined) {
        return headBranch;
    }
    const mainBranch = await getGitBranch(repositoryRoot, 'main');
    if (mainBranch !== undefined) {
        return mainBranch;
    }
    return FALLBACK_BRANCH;
};
const getGitBranch = async function (repositoryRoot, gitRef) {
    try {
        const { stdout } = await execaCommand(`git rev-parse --abbrev-ref ${gitRef}`, { cwd: repositoryRoot });
        return stdout;
    }
    catch {
        // continue regardless error
    }
};
const FALLBACK_BRANCH = 'master';