3. Git branches

Branches in git are "cheap" and easy, they allow to help maintain the information, both locally and remotely.

3.1. Team workflow

This work flow is based on Vicent Driessen and Marcus Geelnard branch strategies, it defines rules how branches are forked, merged and tagged. By having well defined set of branches, the project structure is used as a communication tool, allowing to work simultaneously on different stages of the development.

Main Branches;

    ___A___________AB_____ Master
        \___B_____/ \____  Develop

A represents a commit, then code forked into develop and a commit B was made, develop was the merged back to master AB.

master: Current stable release history, it only contains merges, develop, hot-fix and release branches.
develop: Where new features are merged and tests are performed, if all tests pass is to forked to release.

Development branches;

    _A_______________________AF_______________ Master
      \                    /   \_AFHBH_/       Hotfix
                   __AFHB_/                    Release
       \__________/___________________________ Develop
         \_F_/                                 Feature

feature (f-): Feature only contain isolated features, improvement proposal, code review, integration tests, etc.; Only fork and merge from/to develop, when only local use rebase to keep update with develop branch.
hotfix (h-): Hotfix only contain isolated bugfixes.; Only fork from master, merges back to master and develop.

Code support branches;

    _______________________________AFHB___ Stable-X.Y
    __AF_________________________/________ Master
           \_AFH_/ \            /\         Hotfix
                    \   __AFHB_/  \        Release
    _________________\_/___________\______ Develop

release (r-): Next release, only bug fix's are allowed to be merged.; Major releases fork from develop, merges to master and develop.
stable (stable-): Sable major (X) and minor (Y) release branch, each commit correspond to patch level (Z) with a tag name-(X.Y.Z). Only cherry pick hotfixes from master or next branched security patch level.

3.2. Feature

Create a branch featurex from develop and checkout;

    $ git checkout -b featurex develop

Initial feature commit;

    $ git commit -m "added new feature X"

Other feature commit;

    $ git commit -m "better implementation and tests."

Prepare for testing and merge back;

    $ git checkout featurex
    $ git rebase -i develop

Run test's, fixes are implemented;

    $ git commit -m "feature X tests fix's."

Rebase strategy is cleaner than merge. When pushed to remotes merge strategy can be used or use force push. To run remote tests, code review etc, push branch to server;

    $ git push -u origin featurex

Rename a branch, if all feature branches start by "f-" is easy and quick to type and easy to spot;

    $ git branch -m featurex f-xpto

Rename remote branch;

    $ git push origin :featurex f-xpto
    $ git push origin -u f-xpto

Merge branch feature into develop, first make sure is update with develop and history is clean;

    $ git checkout featurex
    $ git rebase -i develop

    $ git checkout develop
    Switched to branch 'develop'
    $ git merge --no-ff f-xpto
    Updating ea1b82a..05e9557
    (Summary of changes)
    $ git push origin develop

Delete Remote

    $ git push origin :f-xpto

Delete Local;

    $ git branch -D f-xpto

3.3. Release

Software release numbers follow Tom Preston-Werner description;

    projectname-X.Y.Z.tar.xz

X: Major version, backwards incompatible API changes.
Y: Minor version, backwards-compatible changes.
Z: Patch level, backwards-compatible bug and security fixes.

There are patch level or minor new features and major releases. New features releases and major releases fork from develop, code is freeze to let keep adding new features to develop while preparing the code to merge to master and back to develop.

    $ git checkout -b r-1.2.0 develop
    Switched to a new branch "release-1.2.0"
    $ ./bump-version.sh 1.2.0
    Files modified successfully, version bumped to 1.2.0.
    $ git commit -a -m "Bumped version number to 1.2.0"
    [release-1.2 74d9424] Bumped version number to 1.2.0
    1 files changed, 1 insertions(+), 1 deletions(-)

Only documentation or bugfixes are allowed in this branch. When release is ready for production tests merge and push to master;

    $ git checkout master
    Switched to branch 'master'
    $ git merge --no-ff r-1.2.0
    Merge made by recursive.

3.4. Tags

There are two main types of tags, lightweight and annotated. Lightweight tag is a pointer to a specific commit, much like cheap branches. Annotated tags are stored as full objects and allow to sign with gnupg, making it ideal for distributing releases.

Tags are used to mark patch releases, get back in time to make security patches or to mark a new major or minor new release. Tag new release with projectname-version, this allows meaningful ports distfiles when downloading releases from git archives;

    $ git tag -a projectname-1.2.0
    $ git push --follow-tags

Update branch develop with bugfixes from last release, conflict will happen in next step

    $ git checkout develop
    Switched to branch 'develop'
    $ git merge --no-ff r-1.2.0
    Merge made by recursive.
    (Summary of changes)
    $ git push

Delete local and remote;

    $ git tag -d projectname-0.0.12
    $ git push origin :refs/tags/software-name-0.8

List local tags;

    $ git tag --list

3.5. Hotfix

Hotfix are done in master, the only exceptions are release and stable branches. When hot fix is applied to a stable branch is not included in future releases, only needed when cherry pick is hard or impossible. When hot fixes are done on release branches, as described on this document, they have short duration, hot fixes should relate only to new code. To create a hot/bug fix;

    $ git checkout -b h-error-name master

Merge the branches with bug fixes;

    $ git merge --no-ff b-error-xpto
    ...
    $ git commit -m "Commit severe fix"
    ...
    $ git merge --no-ff b-error-xpto
    ...
    $ git commit -m "Commit severe fix"
    ...
    $ git rebase -i master

Merge the hotfix back to master;

    $ git checkout master
    Switched to branch 'master'
    $ git merge --no-ff h-error-name
    Merge made by recursive.

On stable branches cherry pick the commit;

    $ git checkout stable-1.1
    $ git checkout -b r-1.1.2
    $ ./bump-version.sh 1.1.2
    Files modified successfully, version bumped to 1.1.2
    $ git commit -a -m "Bumped version number to 1.1.2"
    $ git cherry-pick h-error-name
    $ git checkout stable-1.1
    $ git merge --no-ff r-1.1.2
    $ git tag -a projectname-1.1.2

Conflicts happen in previews and next step;

    $ git checkout develop
    Switched to branch 'develop'
    $ git merge --no-ff h-error-name
    Merge made by recursive.
    (Summary of changes)

    $ git -D r-1.1.2
    $ git -D h-error-name

Some times is useful to pick the last commit that affected a path on other branch. To achieve this first get last commit that affected the path;

    $ git checkout upstream
    $ git log -n 1 -- path/dir/or/file.c
    $ git checkout stable-3.4
    $ git cherry-pick 9ce8b280e7081ec3c122b228cfa76600251ea6c9

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