VC | 'develop' 'master' workflow

Table of Contents:

• Overview
• Get on a local 'develop' tracking branch
• Simple Centralized workflow on the 'develop' branch
• Transitioning local changes to the 'develop' branch

# Overview

The Trilinos project uses a long-lived branch called 'develop' to conduct basic development. All Trilinos developers directly pull from and push to the shared github 'develop' branch. Then, the 'master' branch is updated from the 'develop' branch when it passes a specific set of builds for a specific set of packages (the set of packages and builds will evolve over time). This is depicted in the below figure:

The motivation for the usage of a 'develop' branch and the full set of mechanics and implications are described in Addition of a 'develop' branch.

For those developers more comfortable with git, all one needs to do is:

• Get on a local 'develop' branch which is tracking 'origin/develop' (see details)
• Pull from, make changes on, and push to the 'develop' branch instead of the 'master' branch (see details)
• If changes are accidentally make to one's local 'master' branch instead of the local 'develop' branch, then just merge the local 'master' branch to the local 'develop' branch and then reset the local 'master' branch (see details).

If a developer understands the above, then they don't need to ready any more on this page. However, if a developer is not clear what is required, then the rest of this page contains the exact detailed information that an average Trilinos developer needs to know in order to transition to and use the 'develop' branch as well as make commits on the local 'develop' branch and push to the shared 'develop' branch. Performing these tasks does not require advanced usage of git. All required commands and steps are described in detail below.

(NOTE: The "bug-fix" workflow elements shown in the above figure are not described below but are described in great detail the above reference. If things go well, then these "bug fix" commits should almost never be needed. But in the rare cases these "bug-fix" commits or revert commits are needed/desired, then more experienced Trilinos git developers can help make those changes.)

# Get on a local 'develop' tracking branch

Modifying the workflow from the Simple Centralized Workflow to use the 'develop' branch instead of the 'master' branch is easy. If the local repo is clean (i.e. no local modifications or untracked files), then one just needs to get on a local 'develop' tracking branch. If the local 'develop' tracking branch has not already been created, then create it using:

$ cd Trilinos/
[ (master)]$ git fetch origin
[ (master)]$ git checkout --track origin/develop
[(develop)]$ 

If the local 'develop' tracking branch was already created (can be seen by running git branch), then just check out that branch using:

$ cd Trilinos/
[ (master)]$ git checkout develop
[(develop)]$ 

# Simple Centralized workflow on the 'develop' branch

Once on the local 'develop' branch which is tracking the remote 'origin/develop' branch, one simply uses the Simple Centralized Workflow using raw git pull, git commit and git push commands, i.e.:

[(develop)]$ git pull                               # from origin/develop
... Make changes (e.g. using emacs or vi) ...
[(develop)]$ git commit -a
[(develop)]$ git status
[(develop)]$ git log --name-status @{u}..HEAD       # review changes
[(develop)]$ git pull                               # from origin/develop
... Test changes (e.g. using checkin-test.py) ...
[(develop)]$ git pull --rebase                      # from origin/develop
[(develop)]$ git push                               # to origin/develop

NOTE: The checkin-test.py script performs the steps from the second git pull after the local modifications are committed to the final git push robustly in a single command.

# Transitioning local changes to the 'develop' branch

The below process applies only to situations where a Trilinos developer has made changes (and perhaps local commits) to the local git repo's 'master' branch and needs to transfer the changes to their local 'develop' branch, where they can be pushed to the github 'develop' branch.

NOTE: These instructions assume that the Trilinos developer is using the simple centralized workflow on the local 'master' branch and has been directly pushing their locally created commits directly to the github 'master' branch. If a more complex workflow is being used (such as using a shared topic branch, or other types of git workflows), then the instructions need to be cusotmized for the specific situation.

Before getting started, every Trilinos developer should set up their local account to use the git usability scripts git-prompt.sh and git-completion.bash and enable git rerere as described here. The shell scripts will make it obvious what local branch a developer is on and git rerere will help with the rebasing and merging commands required to transition local commits.

The process to transition local changes not on the 'develop' branch to the 'develop' branch are:

1) Commit any desired uncommitted changes:

[(master)]$ git add <modified-or-new-files>
[(master)]$ git commit

If there are any remaining changes to tracked files that one does not want to keep, then they can be reverted using:

[(master)]$ git checkout HEAD -- .

If there are untracked files that one does not want to keep, then just delete them manually or do:

[(master)]$ git clean -xdf

or add ignores for them.

2) Checkout the local tracking 'develop' branch:

This step is already described above. That is, either one creates a new local tracking 'develop' branch from scratch (if it has not already been created) with:

[ (master)]$ git fetch
[ (master)]$ git checkout --track origin/develop
[(develop)]$

or one checks out the previously created 'develop' tracking branch and updates it with:

[ (master)]$ git checkout develop
[(develop)]$ git pull   # from origin/develop
[(develop)]$

3) Merge changes from the local 'master' branch to the local 'develop' branch:

[(develop)]$ git merge master   # resolve any merge conflicts

At this point, the merged in commits from the local 'master' branch are safe and will get pushed to the remote github 'develop' branch. These commits will be rebased before the final push as described above. (NOTE: If git rerere is enabled, then any merge conflicts that have already been resolved will be resolved automatically on the final rebase before the final push.)

4) Reset the local 'master' branch

If one will later want to go back to the local 'master' branch, then it is a good idea to reset it to the 'origin/master' branch after the locally updated 'master' branch has been merged into the 'develop' branch as described above. This reset is performed as:

[(develop)]$ git checkout master
[ (master)]$ git reset --hard origin/master

Then one can go back to the 'develop' branch and continue work there with:

[ (master)]$ git checkout develop
[(develop)]$