polyvers 0.0.1a3

==================================================================
Polyvers: Bump independently sub-project versions in Git monorepos
==================================================================

.. _opening-start:
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:alt: Apveyor (Windows) build?
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:version: 0.0.1a3
:updated: 2018-04-02T20:54:46.160562
:Documentation: https://polyvers.readthedocs.io
:repository: https://github.com/JRCSTU/polyvers
:pypi-repo: https://pypi-hypernode.com/project/polyvers/
:keywords: version-management, configuration-management, versioning,
git, monorepo, tool, library
:copyright: 2018 JRC.C4(STU), European Commission (`JRC <https://ec.europa.eu/jrc/>`_)
:license: `EUPL 1.2 <https://joinup.ec.europa.eu/software/page/eupl>`_

A python 3.6+ command-line tool to manage `PEP-440 version-ids
<https://www.python.org/dev/peps/pep-0440/>`_ of dependent sub-projects
hosted in a *Git* `monorepos`_, independently.

When bumping the version of sub-project(s), *polyvers* does the following:

- help you decide the next version of sub-projects, selectively and independently;
- add x2 tagged commits for each project bumped:

- one in-trunk *"Version" commit tags (pvtags)* like ``foo-proj-v0.1.0``,
and another `out-of-trunk (leaf) "Release" commit`_ like ``foo-proj-r0.1.0``;

- engrave the new versions in the source code of bumped-project(s) and
all *dependent* sub-projects, but this happening only in the "leaf"
version-commit;
- build packages out of the later (optionally);
- enforce (customizable) validation rules and run (extensible) hooks.

Additional capabilities and utilities:

- **polyverslib** library code to extract sub-project's version from past tags
(provided a a separate subproject here);

- (``pip install -e <project>``) all subprojects in "develop mode".

- It is still possible to use plain **version tags (vtags)** like ``v0.1.0``,
assuming you have a single project (called hereinafter a *mono-project*)

.. _opening-end:

.. contents:: Table of Contents
:backlinks: top
:depth: 4


.. _usage:

Quickstart
==========
1. Installing the tool, and you get the ``polyvers`` command:

.. code-block:: console

$ pip install polyvers
...
$ polyvers --version
0.0.0
$ polyvers --help
...

$ polyvers status
polyvers: Neither `setup.py` nor `.polyvers(.json|.py|.salt)` config-files found!

.. Note::

There are actually two projects to install, depending on your needs:

- **polyvers** tool, for developing python monorepos,
- **polyverslib**: a python library used by projects developed with *polyvers*
tool to discover their version on runtime from Git.


2. Assuming our *monorepo* project ``/monorepo.git/`` contains two sub-projects::

/monorepo.git/
+--base_project/
| +--setup.py: setup(name='baseproj', ...)
| +--baseproj/__init__.py
| +--...
+--core/
+--setup.py: setup(name='core', ...)
+--core/__init__.py
+--...

...we have to map the *project folders ↔ project-names* using a `traitlets configuration
file <https://traitlets.readthedocs.io>`_ named as
``/monorepo.git/.polyvers.py``:

.. code-block:: python

c.Polyvers.projects = [
{'path': 'base_project'}, # If no 'name' given, extracted from `setup.py`.
{'name': 'core'} # If no `path`, same as `project_name` implied.
]


3. We then set each sub-project to derive its version *on runtime* from latest tag(s),
using this code in e.g. ``/monorepo.git/base_project/baseproj/__init__.py:``:

.. code-block:: python

import polyvers

__title__ = "baseproj"
__version__ = polyvers.version('baseproj')
...


4. We can now use the ``polyvers`` command to inspect & set the same version to all
sub-projects:

.. code-block:: console

$ cd /monorepo.git
$ polyvers status # No sub-project versions yet.
base_project: null
core: null

$ polyvers setver 0.0.0
...
base_project: 0.0.0
core: 0.0.0

$ git lg # Ok, augmented `lg` output a bit here...HEAD --> UPPER branch.
COMMITS BRANCH TAGS REMARKS
======= ====== ==================== ========================================
O latest baseproj-r0.0.0 - x2 tags on "Release" leaf-commit
/ core-r0.0.0 outside-of-trunk (not in HEAD).
O MASTER baseproj-v0.0.0 - x2 tags on "Version" commit
| core-v0.0.0 for bumping both projects to v0.0.0
O - Previous commit, before version bump.

.. Hint::
Note the difference between ``ABC-v0.0.0`` vs ``ABC-r0.0.0`` tags.

In the source code, it's only the "release" commit that has *engraved* version-ids:

.. code-block:: console

$ cat base_project/baseproj/__init__.py # Untouched!
import polyvers

__title__ = "baseproj"
__version__ = polyvers.version('baseproj')
...

$ git checkout latest
$ cat base_project/baseproj/__init__.py
import polyvers

__title__ = "baseproj"
__version__ = '0.0.0'
...

$ git checkout - # to return to master.


5. Now let's add another commit and then bump ONLY ONE sub-project:

.. code-block:: console

$ git commit --allow-empty -m "some head work"
$ polyvers bump 0.0.1.dev baseproj
...
base_project: 0.0.1.dev0
core: 0.0.0+base_project.0.0.1.dev0

$ git lg
COMMITS BRANCH TAGS REMARKS
======= ====== ==================== ========================================
O latest baseproj-r0.0.1.dev0 - The latest "Release" leaf-commit.
/ branch `latest` was reset non-ff.
O MASTER baseproj-v0.0.1.dev0 - The latest "Version" commit.
O - some head work
| O baseproj-r0.0.0 - It's obvious now why "Release" commits
|/ core-r0.0.0 are called "leafs".
O baseproj-v0.0.0
| core-v0.0.0
O

$ git checkout latest
$ cat base_project/baseproj/__init__.py
import polyvers

__title__ = "baseproj"
__version__ = '0.0.1.dev0'
...

$ cat core/core/__init__.py
import polyvers

__title__ = "core"
__version__ = '0.0.0+baseproj.0.0.1.dev0'
...
$ git checkout -

Notice how the the `"local" part of PEP-440
<https://www.python.org/dev/peps/pep-0440/#local-version-identifiers>`_ (statring with ``+...``)
is used by the engraved version of the **un-bumped** ``core`` project to signify
the correlated version of the **bumped** ``baseproj``. This trick is uneccesary
for tags because they apply repo-wide, to all sub-projects.


.. _features:

Features
========
PEP 440 version ids
-------------------
While most versioning tools use `Semantic versioning
<http://semver.org/>`_, python's ``distutils`` native library
supports the quasi-superset, but more versatile, `PEP-440 version ids
<https://www.python.org/dev/peps/pep-0440/>`_, like that:

- Pre-releases: when working on new features::

X.YbN # Beta release
X.YrcN or X.YcN # Release Candidate
X.Y # Final release

- Post-release::

X.YaN.postM # Post-release of an alpha release
X.YrcN.postM # Post-release of a release candidate

- Dev-release::

X.YaN.devM # Developmental release of an alpha release
X.Y.postN.devM # Developmental release of a post-release


Monorepos
---------
When your single project succeeds, problems like these are known only too well:

Changes in **web-server** part depend on **core** features that cannot
go public because the "official" **wire-protocol** is freezed.

While downstream projects using **core** as a library complain about
its bloated transitive dependencies (asking why *flask* library is needed??).

So the time to "split the project has come. But from `lerna <https://lernajs.io/>`_:

Splitting up large codebases into separate independently versioned packages
is extremely useful for code sharing. However, making changes across
many repositories is messy and difficult to track, and testing across repositories
gets complicated really fast.

So a *monorepo* [#]_ [#]_ is the solution.
But as `Yarn <https://yarnpkg.com/blog/2017/08/02/introducing-workspaces/>`_ put it:

OTOH, splitting projects into their own folders is sometimes not enough.
Testing, managing dependencies, and publishing multiple packages quickly
gets complicated and many such projects adopt tools such as ...

*Polyvers* is such a tool.

.. [#] <https://medium.com/@maoberlehner/monorepos-in-the-wild-33c6eb246cb9
.. [#] http://www.drmaciver.com/2016/10/why-you-should-use-a-single-repository-for-all-your-companys-projects/

Out-of-trunk (leaf) "Release" commit
------------------------------------
Even in single-project repos, sharing code across branches may cause merge-conflicts
due to the version-ids "engraved" in the sources.
In monorepos, the versions proliferate, and so does the conflicts.

Contrary to `similar tools`_, static version-ids are engraved only in out-of-trunk
(leaf) commits, and only when the sub-projects are released.
In-trunk code is never touched, and version-ids are reported, on runtime, based
on Git tags (like ``git-describe``), so they are always up-to-date.

Marking dependent versions across sub-projects
----------------------------------------------
When bumping the version of a sub-project the `"local" part of PEP-440
<https://www.python.org/dev/peps/pep-0440/#local-version-identifiers>`_
on all other the *dependent* sub-projects in the monorepo signify their relationship
at the time of the bump.

Lock release trains as "developmental"
--------------------------------------
Specific branches can be selected always to be published into *PyPi* only as
`PEP-440's "Developmental" releases
<https://www.python.org/dev/peps/pep-0440/#developmental-releases>`_, meanining that
users need ``pip install --pre`` to install from such release-trains.
This is a safeguard to avoid accidentally landing half-baked code to users.

Other Features
--------------
- Highly configurable using `traitlets <https://traitlets.readthedocs.io>`_, with
sensible defaults; it's possible to run without any config file in single-project repos.
- Always accurate version reported on runtime when run from git repos
(never again wonder with which version your experimental-data were produced).
- Extensible with bump-version *hooks* (e.g. for validating doctests) TODO: implemented
as `setuptools plugins
<http://setuptools.readthedocs.io/en/latest/setuptools.html#dynamic-discovery-of-services-and-plugins>`_.

Drawbacks & Workarounds
-----------------------
- To ``pip``-install python projects from remote URLs is a bit `more complicated
<https://pip.pypa.io/en/stable/reference/pip_install/#vcs-support>`_::

pip install -e git+https://repo_url/#egg=pkg&subdirectory=pkg_dir

- Set branch ``latest`` as default in GitHub to show engraved sub-project version-ids.


Similar Tools
=============
- The original **bumpversion** project; development stopped after 2015:
https://github.com/peritus/bumpversion
- **bump2version:** active clone of the original:
https://github.com/c4urself/bump2version
- **releash**: another *monorepos* managing tool, that publishes also to PyPi:
https://github.com/maartenbreddels/releash
- **Git Bump** using git-hooks:
https://github.com/arrdem/git-bump
- Search other `34 similar projects in GitHub
<https://github.com/search?l=Python&o=desc&q=bump+version&s=updated&type=Repositories>`_.
- https://github.com/korfuri/awesome-monorepo
- `Lerna <https://lernajs.io/>`_: A tool for managing JavaScript projects
with multiple packages.
- `Pants <https://www.pantsbuild.org/>`_: a build system designed for codebases that:
- Are large and/or growing rapidly.
- Consist of many subprojects that share a significant amount of code.
- Have complex dependencies on third-party libraries.
- Use a variety of languages, code generators and frameworks.



Credits
=======
This package was created with Cookiecutter_ and the `audreyr/cookiecutter-pypackage`_ project template.

.. _Cookiecutter: https://github.com/audreyr/cookiecutter
.. _`audreyr/cookiecutter-pypackage`: https://github.com/audreyr/cookiecutter-pypackage


History
=======

0.0.0 (2018-01-29)
------------------

* First release on PyPI.