Build failures due to detached head ⚓
Builds can fail due to many reasons, and one of those is related to how a build is started and how Git works.
If you start a build manually and you only specify a branch, then
git clone will clone that branch.
If, however, you use webhooks to automatically trigger builds on code changes, a repo host will send the commit hash of the commit which triggered the build webhook and
git-clone will clone that specific commit. This would put the local git instance into detached head state.
Let’s test this locally with a
git checkout COMMITHASH.
$ git checkout 6415740f2e73d65eb85969324d6d66f9a36bc70f Note: checking out '6415740f2e73d65eb85969324d6d66f9a36bc70f'. You are in 'detached HEAD' state. You can look around, make experimental changes and commit them, and you can discard any commits you make in this state without impacting any branches by performing another checkout. If you want to create a new branch to retain commits you create, you may do so (now or later) by using -b with the checkout command again. Example: git checkout -b <new-branch-name> HEAD is now at 6415740... commit message
As you can see from the command’s log, now you are in a detached head state, meaning the head is NOT pointing to the tip of the current branch but to your COMMIT OBJECT. This means you are not on any branch, therefore, you can’t push commits to any branch either at this stage. What you can do in a detached head state is:
- Creating commits.
- Checking if tests have successfully run in this code version.
So to be able to commit and push DIRECTLY TO A BRANCH, you’ll have to check out a branch first. Let’s see how!
The above error message suggests a solution for getting back to a branch from the detached head state. You can get back to a branch by simply check out that branch with
git checkout -b BRANCH. You could also check out that branch (
git checkout BRANCH) before committing and pushing your changes. Please bear in mind that if you chose this option, you might commit on a different state of the code than what was built/tested during the build.
Testing git checkout locally ⚓
Let’s try out the above locally.
A build triggered by a webhook (when a commit hash is available) is similar to doing a
git checkout COMMITHASH
This is how the build log will look like
- RepositoryURL: email@example.com:zoltan-baba/sample-apps-react-native-ios-and-android.git - CloneIntoDir: /Users/vagrant/git - Commit: 4d31f45eb2db037f0143f509872a619f9aac8c09 - Tag: - Branch: testing - BranchDest: - PRID: 0 - PRRepositoryURL: - PRMergeBranch: - ResetRepository: false - CloneDepth: 0 - BuildURL: https://app.bitrise.io/build/349008b006272cac - BuildAPIToken: [REDACTED] - UpdateSubmodules: true - ManualMerge: true git "init" Initialized empty Git repository in /Users/vagrant/git/.git/ git "remote" "add" "origin" "firstname.lastname@example.org:zoltan-baba/sample-apps-react-native-ios-and-android.git" git "fetch" Warning: Permanently added 'github.com,126.96.36.199' (RSA) to the list of known hosts. From github.com:zoltan-baba/sample-apps-react-native-ios-and-android * [new branch] master -> origin/master * [new branch] testing -> origin/testing git "checkout" "4d31f45eb2db037f0143f509872a619f9aac8c09"
If the build is started without a commit hash, only with a branch parameter, that’s similar to:
git checkout BRANCH - RepositoryURL: email@example.com:BanyikAnna/sample-apps-react-native-ios-and-android.git - CloneIntoDir: /Users/vagrant/git - Commit: - Tag: - Branch: master - BranchDest: - PRID: 0 - PRRepositoryURL: - PRMergeBranch: - ResetRepository: false - CloneDepth: 0 - BuildURL: https://app.bitrise.io/build/0be5f085fb1d8d4d - BuildAPIToken: [REDACTED] - UpdateSubmodules: true - ManualMerge: true git "init" Initialized empty Git repository in /Users/vagrant/git/.git/ git "remote" "add" "origin" "firstname.lastname@example.org:BanyikAnna/sample-apps-react-native-ios-and-android.git" git "fetch" "origin" "master" Warning: Permanently added 'github.com,188.8.131.52' (RSA) to the list of known hosts. From github.com:BanyikAnna/sample-apps-react-native-ios-and-android * branch master -> FETCH_HEAD * [new branch] master -> origin/master git "checkout" "master"
You can test both on your own machine and see what you have to do to make the tool you use work with the
git checkout COMMITHASH case.
Version number management ⚓
Managing version numbers is important if you’d like to deploy an app to a marketplace. In this section we’ll give you some tips on how to go about incrementing your build’s version number if your branch is currently on a detached head state.
Incrementing the version number manually ⚓
This solution is the easiest to set up and manage, and works best for app type projects and projects where you release periodically (for example, weekly, monthly), but you don’t do multiple daily production deploys.
You can bump the version number manually, treating it just like any other code change. In this case, we use the
BITRISE_BUILD_NUMBER Env Var as the build number in the app, which does not require committing it into the code and this way you can link every build of the app to the build on bitrise.io.
Using git tags for versioning ⚓
If you don’t want to store the version in the code, you can use git tags for versioning. It doesn’t require a commit to be pushed, only
git tag x.x.x && git push origin tags/x.x.x.
This method suits web projects with continuous deployment the most, where a version number wouldn’t mean much in the code.
Auto-generating a commit ⚓
As discussed above, you cannot push code if you are in detached head state. In this case you can auto-generate a commit to increase the version number AND use our Skip CI feature which will prevent a build from being triggered.