Why is repo sync not checking out the branch I had specified in the manifest file?

Question

Suppose I have the following manifest file for the repo tool (MCVE script is included at the end of this post):

<?xml version="1.0" encoding="UTF-8"?>
<manifest>
  <remote name="repo1" fetch="/tmp/standalone_repo_expt/git.repos" />
  <remote name="repo2" fetch="/tmp/standalone_repo_expt/git.repos" />
  <default remote="repo1" revision="master" />
  <project name="repo1" path="repo1" />
  <project name="repo2" path="repo2"  />
</manifest>

I'm able to run repo init ... followed by repo sync into a brand new directory (i.e., without any prior contents). But when I cd into the resulting repo1 subdirectory (e.g., /tmp/standalone_repo_expt/work_area/myproject/repo1/), and do a git status I see this:

$ git status
Not currently on any branch.
nothing to commit, working tree clean

And then showing what branches are available I see:

$ git branch -a
* (no branch)
  remotes/m/master -> repo1/master
  remotes/repo1/master

Why did repo sync not check out to the default branch (master) that I had specified in the default tag in the manifest file?

Similar questions

This is similar to Why doesn't git repo checkout the branch specified? but is not quite the same issue. My issue is that no branch is checked out, and that seems wrong. I should not have to do anything else other than the repo sync, and I should not have to run git checkout master in all of the repositories managed by that manifest file.

This also seems similar to https://stackoverflow.com/a/66264612/257924 but using repo init -b master does not do what I want either (has no effect on this problem of the repositories not being checked out to the specified branch).

https://stackoverflow.com/a/16917618/257924 gets close to answering this question, but does not explain why git branch -a does not contain the master branch right after the repo sync.

Repo tool version

The repo tool was pulled from source directly on 2021-11-15 via:

curl https://storage.googleapis.com/git-repo-downloads/repo > /tmp/standalone_repo_expt/bin/repo

and the PATH set to include /tmp/standalone_repo_expt/bin.

MCVE script

#!/bin/bash

function generate_repo {
  local repo_num="$1"
  mkdir -p /tmp/standalone_repo_expt/git.repos/repo$repo_num.git
  cd /tmp/standalone_repo_expt/git.repos/repo$repo_num.git
  git init --bare

  mkdir -p /tmp/standalone_repo_expt/work_area
  git clone /tmp/standalone_repo_expt/git.repos/repo$repo_num.git || {
    echo ERROR: git clone /tmp/standalone_repo_expt/git.repos/repo$repo_num.git
    exit 1
  }

  (
    cd repo$repo_num
    touch repo$repo_num.README
    git add repo$repo_num.README
    git commit -m "Add repo$repo_num.README"
    git push origin
  )

  (
    mkdir -p /tmp/standalone_repo_expt/work_area/repo$repo_num.test_clone
    cd /tmp/standalone_repo_expt/work_area/repo$repo_num.test_clone
    git clone /tmp/standalone_repo_expt/git.repos/repo$repo_num.git
    ls -ld repo$repo_num/*
    cd repo$repo_num
    git status
  )
}

# Remove the entire set of git repos for reproducable execution:
rm -rf /tmp/standalone_repo_expt

# Generate the git repositories, that we wish to combine into one
# larger directory, using the repo tool:
generate_repo 1
generate_repo 2

# Install the repo tool from source, not using any package managers:
mkdir -p /tmp/standalone_repo_expt/bin
curl https://storage.googleapis.com/git-repo-downloads/repo > /tmp/standalone_repo_expt/bin/repo 
test -s /tmp/standalone_repo_expt/bin/repo || {
  echo "ERROR: Failed to download repo tool into /tmp/standalone_repo_expt/bin/repo"
  exit 1
}
chmod a+rx /tmp/standalone_repo_expt/bin/repo
PATH="/tmp/standalone_repo_expt/bin:${PATH}"
which repo >& /dev/null || {
  echo "ASSERTION FAILED: Failed to install the repo tool."
  exit 1
}

# Create the git repository that houses the manifest that are needed
# by the repo tool that reference the git repositories generated
# above:
mkdir -p /tmp/standalone_repo_expt/git.repos/manifests.git
cd /tmp/standalone_repo_expt/git.repos/manifests.git
git init --bare

# Clone the manifest bare repo so we can add the manifest file, and
# push it back:
cd /tmp/standalone_repo_expt/work_area
git clone /tmp/standalone_repo_expt/git.repos/manifests.git || {
  echo ERROR: git clone /tmp/standalone_repo_expt/git.repos/manifests.git failed
  exit 1
}
cd manifests
cat > default.xml <<EOF.manifest
<?xml version="1.0" encoding="UTF-8"?>
<manifest>
  <remote name="repo1" fetch="/tmp/standalone_repo_expt/git.repos" />
  <remote name="repo2" fetch="/tmp/standalone_repo_expt/git.repos" />
  <default remote="repo1" revision="master" />
  <project name="repo1" path="repo1" />
  <project name="repo2" path="repo2"  />
</manifest>
EOF.manifest

cat default.xml

git add default.xml
git commit -m "Manifest file used by the repo tool"
git push origin || {
  echo ERROR: git push origin failed
  exit 1
}

set -x
mkdir -p /tmp/standalone_repo_expt/work_area/myproject
cd /tmp/standalone_repo_expt/work_area/myproject
repo init /tmp/standalone_repo_expt/git.repos/manifests.git
repo sync

cd repo1
pwd
ls -l
git status

Answer 1

repo doesn't create a local branch for you. When you check out a remote branch you'll end up with a detached head (since you can't make commits on the remote branch anyway).

https://groups.google.com/g/repo-discuss/c/yPoPazTRgMA