Added bootstrap.rst

doc/source/bootstrap.rst

+Bootstrapping the Chromium Infra Repo
+=====================================
+
+The infra/infra repo uses python [wheel files][1], [virtualenv][2] and [pip][3]
+to manage dependencies. The process for bootstrapping these is contained
+entirely within the bootstrap directory.
+
+1: https://www.python.org/dev/peps/pep-0427/
+2: https://github.com/pypa/virtualenv
+3: https://github.com/pypa/pip
+
+
+TL;DR - Workflows
+~~~~~~~~~~~~~~~~~
+
+Setting up the env with already-built-deps
+++++++++++++++++++++++++++++++++++++++++++
+
+  gclient sync  
+  # OR
+  gclient runhooks
+
+Adding a new dep
+++++++++++++++++
+Say we want to add a stock `my_pkg` python package at version 1.2.3:
+
+If it comes from a tarball::
+
+  $ ./bootstrap/ingest_source.py <tarball>
+  ...
+  deadbeefdeadbeefdeadbeefdeadbeef.tar.gz
+
+If it comes from a repo:
+
+File a ticket to have it mirrored (no matter what VCS!)
+to ``chromium.googlesource.com/external/<repo_url>``
+
+Grab the git commit hash of the commit to build: badc0ffeebadc0ffeebadc0ffeebadc0
+
+Then add the actual dep::
+
+  $ edit bootstrap/deps.pyl  # add a new entry (see the 'deps.pyl' section)
+  ...
+    'my_pkg' : {
+      'version': '1.2.3',
+      'build': 0,  # This is the first build
+      'gs':  'deadbeefdeadbeefdeadbeefdeadbeef.tar.gz',  # if tarball
+      'rev': 'badc0ffeebadc0ffeebadc0ffeebadc0',         # if repo
+    }
+  ...
+
+Then build it::
+
+  $ ./bootstrap/build_deps.py
+  # builds and uploads my_pkg-1.2.3-0_deadbeef...-....whl to google storage
+
+**If your dep is not pure-python, you will have to run ``build_deps.py`` for 
+each platform.**
+
+
+If your dep needs special treatment
++++++++++++++++++++++++++++++++++++
+Do everything in the 'Adding a new dep' section, but before running
+``build_deps.py``, add a file ``bootstrap/custom_builds/{wheel package name}.py``.
+This file is expected to implement::
+
+  def Build(source_path, wheelhouse_path)
+
+See `custom builds`_ below for more detail.
+
+
+``bootstrap.py`` (a.k.a. "I just want a working infra repo!")
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Run ``gclient runhooks``. Under the hood, this runs::
+
+  ./bootstrap/bootstrap.py --deps_file bootstrap/deps.pyl
+
+This creates a virtualenv called ``{repo_root}/ENV`` with all the deps contained
+in ``bootstrap/deps.pyl``. You must be online, or must already have the wheels 
+for your system cached in ``{repo_root}/.wheelcache``.
+
+If you already have an ``ENV``, ``bootstrap.py`` will check the manifest in
+``ENV`` to see if it matches `deps.pyl`_ (i.e. the diff is zero). If it's not,
+then ``ENV`` will be re-created *from scratch*.
+
+``{repo_root}/run.py`` will automatically use the environment ``ENV``. It is an
+error to use ``run.py`` without first setting up ``ENV``.
+
+
+`deps.pyl`
+~~~~~~~~~~
+This file is a python dictionary containing the exact versions of all Python
+module dependencies. These versions are the standard upstream package versions
+(e.g. '0.8.0'), plus the commit hash or sha1.{ext} of an ingested source bundle
+(see ``inject_source.py``).
+
+The format of this file is ``{'package_name': <values>}``. This file is a Python
+`ast literal <https://docs.python.org/2/library/ast.html#ast.literal_eval>`_, so
+comments are allowed and encouraged. 
+
+Note that the ``package_name`` key is the pip-reported name (the one set in 
+``setup.py``). It may be different from the name used for import, and for the
+wheel.
+
+Values are:
+  * version: The pip version of the module
+  * build: An integer representing which build of this version/hash. If you
+      modify the _way_ that a requirement is built, but not the source hash, you
+      can bump the build number to get a new pinned dependency.
+
+And either:
+  * ``rev``: The revision or sha1 of the source for this module.
+    The repo is
+      ``git+https://chromium.googlesource.com/infra/third_party/{package_name}``
+  * ``gs``: ``{sha1}.{ext}`` indicates file
+    ``gs://chrome-infra-wheelhouse/sources/{sha1}.{ext}``. The sha1 will be
+    checked against the content of the file.
+
+And optionally:
+  * ``implicit``: A boolean indicating that this dep should only be installed as
+    a dependency of some other dep. For example, you want package A, which
+    depends on package Z, but you don't really care about Z. You should mark
+    Z as ``implicit`` to allow it to be pinned correctly, but not to
+    deliberately install it.
+
+
+``ingest_source.py``
+~~~~~~~~~~~~~~~~~~~~
+Some python modules don't have functional python repos (i.e. ones that pip
+can natively clone+build), and thus ship their source in tarballs. To ingest
+such a tarball into the infra google storage bucket, use
+  `ingest_source.py /path/to/archive`.
+This will print the value for the 'gs' key for a `deps.pyl` entry.
+
+
+`build_deps.py` / rolling deps
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Any time a new dependency/version is introduced into ``deps.pyl``, you must run
+``build_deps.py``. If the dependency is a pure-Python dependency (i.e. no compiled
+extensions), you only need to run it once on CPython 2.7. You can tell that it's
+a pure python module by looking at the name of the wheel file. For example::
+
+  requests-2.3.0-py2.py3-none-any.whl
+
+Is compatible with Python 2 and Python 3 (py2.py3) any python ABI (none), and
+any OS platform (any).
+
+If the module does contain compiled extensions, you must run ``build_deps.py``
+on the following systems (all with CPython 2.7):
+  * OS X 10.9 - ``x86_64``
+  * Windows 7 - ``x86_64``
+  * Linux     - ``x86_64``
+
+TODO(iannucci): Add job to build wheels on all appropriate systems.
+
+Once a wheel is sucessfully built, it is uploaded to
+``gs://chrome-python-wheelhouse/wheels`` if it is not there already.
+
+Running ``build_deps.py`` will only attempt to build dependencies which are
+missing for the current platform.
+
+``build_deps.py`` assumes that it can find ``gsutil`` on ``PATH``, so go ahead
+and install it appropriately for whichever platform you're on. You will also
+need write access to the ``chrome-python-wheelhouse`` bucket.
+
+
+custom builds
+~~~~~~~~~~~~~
+Sometimes building a wheel is a bit trickier than ``pip wheel {repo}@{hash}``. In
+order to support this, add a script named ``custom_builds/{name}.py``. This module
+should have a function defined like::
+
+  def Build(source_path, wheelhouse_path)
+
+Where ``source_path`` is a string path to the checked-out / unpacked source code,
+and ``wheelhouse_path`` is a string path where ``build_deps.py`` expects to find
+a ``.whl`` file after Build completes.
+
+Note that your Build function will actually need to invoke pip manually.
+Currently you can get the path for pip by doing: ``os.path.join(sys.prefix,
+'bin', 'pip')``, and you can invoke it with subprocess (see
+https://code.google.com/p/chromium/codesearch#chromium/infra/bootstrap/custom...
+as an example). 
+
+
+rolling the version of wheel
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Since wheel is a package needed to build the wheels, it has a slightly different
+treatment. To roll wheel, bump the version in deps.pyl, and then run
+``bootstrap_wheel_wheel.sh``
+to build and upload the wheel for ``wheel`` pinned at the version in ``deps.pyl``.
+
+Once you do that, ``build_deps.py`` will continue working as expected.
+
+
+Building deps on Windows
+~~~~~~~~~~~~~~~~~~~~~~~~
+TODO(iannucci): actually implement this
+
+Windows builds require a slightly more care when building, due to the
+complexities of getting a compile environment. To this effect, ``build_deps.py``
+relies on the ``depot_tools/win_toolchain`` functionality to get a hermetic
+windows compiler toolchain. This should not be an issue for chromium devs
+working on windows, since they should already have this installed by compiling
+chromium, but it's something to be aware of.
+
+
+modified (non-upstream) deps
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+If it is necessary to roll a patched version of a library, we should branch it
+in the infra googlesource mirror. This branch should be named ``{version}-cr``,
+and will build packages whose version is ``{version}.{cr_version}`` (e.g. modify
+``setup.py`` on this branch to add an additional component to the version
+field).
+
+For example, given the package ``jane`` at version ``2.1.3``, we would create
+a branch ``2.1.3-cr``. On this branch we would commit any changes necessary to
+``2.1.3``, and would adjust the version number in the builds to be e.g.
+``2.1.3.0``.
+
+