What causes "' + branchName + ' is not a branch!" in pcottle/learnGitBranching?

Create or fetch the branch first (git branch / git fetch)

pcottle/learnGitBranching · error · GitError

' + branchName + ' is not a branch!

Error message

' + branchName + ' is not a branch!

What it means

assertBranchIsRemoteTracking first unescapes the branch name and throws this GitError when engine.resolveID returns null — the branch does not exist at all in the engine.

Source

Thrown at src/js/git/commands.js:103

};

var assertOriginSpecified = function(generalArgs) {
  if (!generalArgs.length) {
    return;
  }
  if (generalArgs[0] !== 'origin') {
    throw new GitError({
      msg: intl.todo(
        generalArgs[0] + ' is not a remote in your repository! try adding origin to that argument'
      )
    });
  }
};

var assertBranchIsRemoteTracking = function(engine, branchName) {
  branchName = crappyUnescape(branchName);
  if (!engine.resolveID(branchName)) {
    throw new GitError({
      msg: intl.todo(branchName + ' is not a branch!')
    });
  }
  var branch = engine.resolveID(branchName);
  if (branch.get('type') !== 'branch') {
    throw new GitError({
      msg: intl.todo(branchName + ' is not a branch!')
    });
  }

  var tracking = branch.getRemoteTrackingBranchID();
  if (!tracking) {
    throw new GitError({
      msg: intl.todo(
        branchName + ' is not a remote tracking branch! I don\'t know where to push'
      )
    });
  }

View on GitHub (pinned to 5b09d0ff96)

Solutions

Create or fetch the branch first (git branch / git fetch)
Double-check spelling against git branch output

Example fix

// before
git push origin feautre
// after
git push origin feature

Defensive patterns

Strategy: validation

Validate before calling

var name = crappyUnescape(branchName); if (!engine.resolveID(name)) { /* create/fetch or reject */ }

Type guard

function branchExists(engine, name) { return !!engine.resolveID(crappyUnescape(name)); }

Prevention

Autocomplete branch names instead of free-text input
git fetch before pushing to new branches

When it happens

Trigger: Calling a push/fetch config that runs assertBranchIsRemoteTracking with a typo'd or nonexistent branch name, e.g. git push origin maain.

Common situations: Typos; branch was never created; branch exists only on origin and was never fetched.

Related errors

AI-assisted analysis of pcottle/learnGitBranching@5b09d0ff96 (2026-08-27). Data as JSON: /api/errors/3848f5f2c4b19d66. Report an issue: GitHub.