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This page amends the Devmanual's Patches article and Article description::describes how to create a source code patch.

Creating a patch

A source code patch for an existing package can easily be created using git. Of course for doing so, dev-vcs/git needs to be installed.

Step 1: Unpack the questionable package using the ebuild command:

user $ebuild $(portageq get_repo_path / gentoo)/sys-fs/lvm2/lvm2-2.02.145-r2.ebuild clean unpack
...
>>> Unpacking source...
>>> Unpacking LVM2.2.02.145.tgz to /var/tmp/portage/sys-fs/lvm2-2.02.145-r2/work
>>> Source unpacked in /var/tmp/portage/sys-fs/lvm2-2.02.145-r2/work

Step 2: Step into the package directory which was created inside work:

user $cd /var/tmp/portage/sys-fs/lvm2-2.02.145-r2/work/LVM2.2.02.145/

In case the unpacked turns out to be a git directory, steps 3 and 4 can be skipped. If not, don't skip.

Step 3: Initialize the unpacked package sources as a git repository:

user $git init
Initialized empty Git repository in /var/tmp/portage/sys-fs/lvm2-2.02.145-r2/work/LVM2.2.02.145/.git/

Step 4: Add all the existing files to git and do a commit:

user $git add .
user $git commit

Step 5: Do the necessary changes. Change one file or even more. Of course, the needed changes should be known.

user $sed -e 's/MAKEDEV:-"debian"/MAKEDEV:-"gentoo"/' -i scripts/lvm2create_initrd/lvm2create_initrd

Step 6: When changes are done, let git show the diff and tee it into the patch file:

user $git diff | tee /tmp/foobar.patch
diff --git a/scripts/lvm2create_initrd/lvm2create_initrd b/scripts/lvm2create_initrd/lvm2create_initrd
index 6e70c55..1e46b5e 100644
--- a/scripts/lvm2create_initrd/lvm2create_initrd
+++ b/scripts/lvm2create_initrd/lvm2create_initrd
@@ -57,7 +57,7 @@ DEVRAM=/tmp/initrd.$$
 BINFILES=${BINFILES:-"`which lvm` `which bash` `which busybox` `which pivot_root`"}
 BASICDEVICES=${BASICDEVICES:-"std consoleonly fd"}
 BLOCKDEVICES=${BLOCKDEVICES:-"md hda hdb hdc hdd sda sdb sdc sdd"}
-MAKEDEV=${MAKEDEV:-"debian"}
+MAKEDEV=${MAKEDEV:-"gentoo"}
 
 # Uncomment this if you want to disable automatic size detection
 #INITRDSIZE=4096
Note
According to Devmanual the patch should be cleaned from metadata. So the command could be enhanced like:
git diff | grep -v '^diff\|^index' | tee /tmp/foobar.patch

Adjusting a malformed patch

TortoiseGit and Git for Windows

Patches generated by Tortoise Git and Git for Windows are padded with additional information that patch does not understand.

FILE PATCH.patchTypical Tortoise Git/Git for Windows Patch
From HASH Day Mon DD hh:mm:ss YYYY
From: AUTHOR <AUTHOR@E-MAIL.TLD>
Date: Day, DD MMM YYYY hh:mm:ss +hhmm
Subject: [PATCH] COMMIT MESSAGE

---
 PATH/TO/FILE.EXT  1 +
 1 file changed, 1 insertion(+)

diff --git a/PATH/TO/FILE.EXT b/PATH/TO/FILE.EXT
index HA..SH CODE
--- a/PATH/TO/FILE.EXT
+++ b/PATH/TO/FILE.EXT
@@ -56,6 +56,7 @@ 
+  some new code
-  some old code
-- 
VERSION.windows.REVISION

The individual generating the patch has to strip these additional lines to make a viable patch file.

FILE PATCH.patchAcceptable Tortoise Git/Git for Windows Patch
--- a/PATH/TO/FILE.EXT
+++ b/PATH/TO/FILE.EXT
@@ -56,6 +56,7 @@ 
+  some new code
-  some old code

Nesting

If the file(s) being patched are not unpacked into the root of the working directory, PATH/TO/A/FILE, but rather some sub-directory of the working directory, SOME/OTHER/PATH/TO/A/FILE, then the patch must be modified to accommodate it.

FILE PATCH.patch
--- a/SOME/OTHER/PATH/TO/FILE.EXT
+++ b/SOME/OTHER/PATH/TO/FILE.EXT
...
Note
This is necessary for, atleast, Go based ebuilds which nest the source code under the repository path e.g. http://git.com/project/repository gets unpacked into the working directory under src/git.com/project/repository

See also

  • /etc/portage/patches — provide a way for users to apply patches to package source code
  • User:Veremit/Patch_format
  • GLEP 25 - Technical information about the formal inclusion and usage of patches within portage.

External resources

  • How to write clean patches when not using git-format-patch.
  • base.eclass - Describes how ebuilds should use PATCHES=( "${FILESDIR}/mypatch.patch" "${FILESDIR}/patches_folder/" )

References


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