Readme: Description to add a repo for reproducible builds

BCS 746-000016

README.md

@@ -22,6 +22,31 @@ via the CI environment variable `GITBOT_TOKEN` (set under project's settings ->
 defined.
 
 
+### Workflow to add a repository to SRCREV.conv for reproducible bitbake builds
+Some bitbake recipes are set to `SRCREV = "${AUTOREV}"`. To enable reproducible
+builds, the current revision is written to the SRCREV.conf file. This file is
+part of the manifest repo, which is used for release tags. This workflow adds
+the a gitlab pipeline to the project that automatically sets the current
+version in the SRCREV.conf file.
+1. Add the gitlab-ci repo as submodule to the project by using the correct relative path\
+`git submodule add ../../yocto/infrastructure/gitlab-ci .gitlab-ci`
+1. Add an approriate .gitlab-ci.yml file. For example, copy it from the repository
+[egalxi2c][4]. Modify the following variables in the file:
+	*  MASTER\_BRANCH\_PROJECT: Set the project master branch
+	*  BB\_RECIPE\_NAME: Set the name of the bitbake recipe
+1. Create a corresponding entry in the SRCREV.conf file of the manifest repo\
+`SRCREV_pn-<bitbake-recipe> = "<current-commit-hash>"`
+
+**Repository settings**
+1. Verify that the merge strategy is set to *Fast-forward merge*
+(General -> Merge requests -> Merge method)
+1. Enable the CI/CD functionality for the repository
+(General -> Visibility, project features, permissions -> CI/CD)
+1. Check that the default branch is protected and that *Maintainers + Developers*
+are allowed to merge (Repository -> Protected branches)
+
+
 [1]: https://git-scm.com/book/en/v2/Git-Tools-Submodules
 [2]: https://docs.gitlab.com/ee/user/profile/personal_access_tokens.html
 [3]: https://gitlab.com/garz-fricke
+[4]: https://gitlab.com/SECO-Northern-Europe/kernel/modules/egalaxi2c