Project:Toolchain/Patchsets with Git

This page describes in detail how the sys-libs/glibc patchsets have been migrated to Git. Hopefully we'll at some point use the same or a very similar system for all parts of toolchain (ie., gcc, binutils, ...).

Regular upstream development
The libc git repository has a master branch where current development takes place. On this master branch, releases are tagged as, e.g, glibc-2.26. From each release tag, a stable / backport branch starts with name release/2.26/master.

Upstream git repository:

Vendor branches and tags
The following branches and tags used to be in upstream git. Right now I am pushing them to a separate github repository, but I'll try to eventually get access to upstream git again.

Github git repository:

Gentoo has a vendor branch gentoo/2.26, which branches off at the upstream glibc-2.26 tag. On this branch the commits corresponding to Gentoo ebuild releases are tagged as gentoo/glibc-2.26-0, where in this case 0 is the patchset number. When upstream makes a new release, say glibc-2.27, a new such branch gentoo/2.27 shall be created starting at that tag, and the existing gentoo/2.26 head be rebased ont it to forward-carry Gentoo-specific patches.

Setting yourself up for development basically means

Making patches
Making patches is easy; just add commits to one of our vendor branches as e.g. gentoo/2.26.

Usually they should be cherry-picked from the upstream stable branch release/2.26/master or the upstream development branch master. In rare cases it may also make sense to add more Gentoo-specific stuff.

Any commit where the commit message starts with [no-patch] will not generate a patch; this is useful for changes in the extra Gentoo files as e.g. the patchset generation script.

Making a patchset
This generates from the current head of gentoo/2.26 a patchset tarball named, and tags the current head of gentoo/2.26 as gentoo/glibc-2.26-1.


 * Please read the script before using it!
 * Make sure your gpg is working for the signed tag!
 * Any commit where the commit message starts with [no-patch] will not generate a patch.
 * Uploading the tarball and pushing stuff to git still must be done manually.
 * So far this infrastructure only exists for 2.26 and 2.25; earlier branches on request.

Where

 * The upstream git repository is
 * The gentoo git repository is

Versioning

 * The upstream release branch is usually named as binutils-2_29-branch
 * The upstream release tags usually looks like binutils_2_29_1
 * The Gentoo branches are named gentoo/binutils-2.29.1 (since we might one day also make patchsets for gdb)
 * The Gentoo patchset tags look like gentoo/binutils-2.29.1-2
 * Since there are irregularities in the release tag naming, you can override them by creating a tag gentoo/binutils-2.29.1-upstream and that will be used as reference for the tarball instead.

Patches
Gentoo branches are occasionally rebased on top of upstream branches. Gentoo-specific patches contain "Gentoo: " prefix. Gentoo patches are initially maintained in gentoo/binutils-9999 branch and later cherry-picked into release branches.

Notes:
 * Upstream pushes a daily automated commit onto each branch, increasing the date in a file. make-tarball.sh sskips date bumping patches when tarball is done. This eases patch rebasing.
 * The "development flag" is a variable set to "true" in git and to "false" in tarballs. Since occasionally patches touch that (while not yet released), we add a patch 0000-... that makes it true, and a patch 9999-... that makes it false again... We definitely do not want it true since it adds -Werror and makes the soversion of libbfd contain the date.

How to cut a new patchset
To create new branch and cut first patchset you need to:
 * create a new gentoo granch based on upstream branch
 * apply gentoo-specific patches on top (usually from gentoo/binutils-9999 branch).
 * tag and tarball
 * push tags and branches

Example session:

To cut new patchset on existing branch you need to:
 * [optional] rebase gentoo-specific branch on top of upstream branch to pull in fresh patches
 * apply new gentoo-specific patches (or cherry-pick from gentoo/binutils-9999 anew)
 * tag and tarball.
 * push tags and branches

Example session: TODO

sys-devel/gcc
Gentoo's gcc patches live at https://gitweb.gentoo.org/proj/gcc-patches.git/

These are just versioned contents normally seen  subtree.

adding new patch
Every Gentoo developer has access to push patches to the patch tree.


 * drop a patch to versioned directory, like 8.2.0/gentoo/
 * add an entry to README.history, like 8.2.0/gentoo/README.history
 * [optionally] cut new patchset with

See README files for more details.