/etc/portage/patches

User patches provide a way for users to apply patches to ebuilds. This is useful for the rare cases of site-specific patches, but also for applying upstream patches to unresolved bugs or testing patches before sending them to upstream or to the Gentoo bug tracker.

Since EAPI=6, this feature is provided by the default src_prepare as shown in line 46 here which calls. Prior to EAPI=6, it was provided either by calling  explicitly or by inheriting an eclass and relying on its default implementation of. Current Gentoo policy does not require ebuilds to use. In EAPIs before EAPI=6, its usage is at the package maintainer's discretion. But there is also a way to enable it for all ebuilds that don't explicitly allow user patching.

Adding user patches
First choose the location for the patches, depending on the package name and the version(s) it is intended for. Use the following locations and optionally append  to any of them:



Examples:



Example
The next example shows a very simple patch for of.

The package that needs a patch will be unpacked using the command:

Any for the user patch needs to refer to the just created directory, so cd into it:

Say were the file to be changed. So it should be copied to (or somwere else):

Make the modifications to the copy:

After having modified the copy, check the :

Of course, still the directory for the patch needs to be created:

Now the directory is ready drop in the patches. Only files with suffix are considered and they are applied in the order determined by their name.

Repeat the and create the patch file:

It is imporant that the first line of the file refers to the S directory created by unpacking.

Note that  attempts to apply them repeatedly with a prefix stripped up to a different number of slashes. However,  used in EAPI=6 defaults to using the -p1 depth for patches. So to satisfy both, it is recommended to use the -p1 depth format where the first directory listed is ignored.

Once the patch gets merged to the ebuild repository, do not forget to remove it from the directory. Otherwise next time compiling the ebuild might fail.

Using a git directory as a source of patches
Instead of creating the directory, a symlink can be created to a git directory on the system.

Now, in the git directory, perform the usual work. After finishing remove all patches from the previous run and use git format-patch to create a patchset from the branch based on another known branch.

This solution relies on the fact that only files ending with are processed in the patch directory.

Enabling /etc/portage/patches for all ebuilds
If an ebuild does not call, but user patches are still needed to be applied, it is possible to use /etc/portage/bashrc and hooks provided by Portage. Candidates are,   or. The first two have the advantage of being run before  (or similar) and the last two have the advantage of being run in the right directory, so only   shares those advantages.

Normally only ebuilds inheriting  can access , so one would need to test for its presence and non-eutils ebuilds would not get patched at all. There is a trick of pulling in only the necessary bits from, running  and dropping them.

With  and the above trick, changing directories do not need to be played with, all ebuilds can be supported whether they import   or not, and the patches will applied as soon as possible in the chain. While it might still be better to have this feature as part of Portage, the following snippet should cover everyday needs pretty well.

External resources

 * eutils.eclass: Disable epatch_user in EAPI 6. - EAPI 6 has eapply_user which should be used instead.
 * The Ultimate Guide to EAPI 6
 * Patching with epatch - Patching within ebuilds, from devmanual.gentoo.org