debian/patches
Since new 3.0 source formats have been adopted, this page serves as a historic record leading to 3.0 format and this can be used as a reference for people converting packages to 3.0 (quilt) format using data found in debian/patches. See Projects DebSrc3.0.
(This page stemmed from the following discussion on debian-devel in January 2008: alpine.DEB.1.00.0801250818360.5187@wr-linux02. It also includes ideas from the discussion #250202 about the Policy.)
Existing systems
General characteristics
Patch system |
Location of the patches |
How to deactivate a patch |
Accepts diff -u output |
Advantage |
debian/patches |
Remove its name from debian/patches/00list |
Header needs to be added |
Can do scripting |
|
debian/patches |
Remove its name from debian/patches/series |
Yes |
Suitable for generating patches on any size codebase. Advanced VCS-like features. |
|
cdbs simple-patchsys |
debian/patches |
Remove its .diff or .patch suffix |
Yes |
Simple |
debian/patches in .debian.tar.gz file |
Rename to include a non-word non-hyphen character |
Yes |
Native to dpkg as 2.0 format |
|
debian/patches in .debian.tar.gz file |
Rename to include a non-word non-hyphen character |
Yes |
Native to dpkg as 3.0 (quilt) format |
|
debian/patches |
Remove it from the directory |
Yes |
Patches applied in ASCIIbetical order, no series file. Tarball-in-tarball (if you're in to that). |
Packages using dpatch system can be converted easily to quilt system which has better supports by other softwares, e.g. guilt for git.
Patching/unpatching targets includeable in debian/rules
File |
Package |
To patch |
To depatch |
/usr/share/dpatch/dpatch.make |
dpatch |
patch |
unpatch |
/usr/share/quilt/quilt.make |
quilt |
patch |
unpatch |
/usr/share/cdbs/1/rules/patchsys-quilt.mk |
quilt |
patch |
unpatch |
/usr/share/cdbs/1/rules/simple-patchsys.mk |
cdbs |
patch |
unpatch |
/usr/share/cdbs/1/rules/dpatch.mk |
cdbs |
patch |
unpatch |
Note that in the case of quilt it may be better to use $(QUILT_STAMPFN) since patch is a phony target.
Limitations
Users of a source package need the unpacked source not ready for compilation, but ready for inspection and modification. The two major use cases are application of (minor) local modifications (security fixes, compile time options) and manual or automated inspection of the source code (auditing, searching). This should be possible without installing additional packages besides dpkg-dev.
It has been discussed that the use of patch systems was making the work of porters, NMUers, security and QA teams difficult for several reasons:
- The profusion of patch systems. People would have to learn them all and to be able to detect which one is used in the package they are working on.
The difficulty to repack the sources. If direct modifications of source pacakages block the target unpatch, and if this target is called by clean, dpkg-buildpackage will fail.
It is unclear whether Wig&Pen will be implemented and if yes, when. Some patch systems are not yet adapted to this format yet.
Documents such as /usr/share/doc/debian/source-unpack.txt do not warn that modifications to the freshly unpacked sources can break the patching step.
Proposed improvements
Simply document how to patch the sources in a file called README.source, a template of which could be provided in the package of the patch system used.
- Standardise the interface of the patch systems.
Use a single wrapper, possibly mandatory.Bugs: 4588 et. al.
- "Qualify" the systems which are widespread and durable, and discourage the use of others.
Make dpkg-source apply the patches automagically after unpacking the sources (using internal procedures).
Alternatively, make dpkg-source issue an informative message if it detects that a patch system is used.
Ship the sources patched (the clean target would call patch). Drawback: it bloats the diff.gz.
Implement a target called patched, that provides sources in such a state that calling debian/rules binary will not revert changes introduced.
Rejected ideas
Make dpkg-source call the patching rule:
- This is a security threat;
- it would require the build-dependencies of a package to be installed.
Using a VCS (instead of patch system) to track changes
Keeping a whole package, including upstream sources, in a version control system (VCS) is often used as a method of managing the modification to upstream sources.
Comparison between the two paradigms
debian/patches |
VCSes |
Changes to upstream sources are divided in logical blocks that are the patches. |
Changes to upstream sources are divided into logical blocks that are groups of commits. |
dpkg-buildpackage can fail after modifications of the sources |
dpkg-buildpackage can not be blocked by the impossibility to unpatch the sources. |
The diff.gz file only contains files located in the debian directory |
Informations conveyed by defining groups of commits is not reflected in the diff.gz file. |
Well documented in beginners tutorials, strong tradition in packaging teams. |
No tutorials for beginners, new and not widespread yet. |
Repositories can be limited to contain only the debian directory. |
Need to keep the upstream sources in a VCS as well. Not true in my experience. What's the justification for this assertion? --BenFinney |
Some systems, such as dpatch allow scripting. |
Changes are systematically applied. |
Of course, the use of VCS have other advantages, but this table focuses on the perspective of their substitution to patch management systems.
I track my packaging changes in a VCS, and am not required to keep upstream source in VCS. What prevents users of a VCS from keeping only debian/ in the VCS repository, and using e.g. bzr-buildpackage --merge to merge with the separate upstream source? --BenFinney 2008-10-06
Previous unanswered questions
- Groups of commits can be more messy that a well-documented patch: while a patch can be modified, a commit can only be reverted by another commit, adding even more complexity to the group of commit. How can the information contained in the logical breakdown of the modifications to upstream in a set of patches can be conveyed in the VCS paradigm? -- This may still be a future question.
- The repository of packaging teams can contain up to hundreds of packages. How can they stay slim if they must contain upstream sources? -- This is an orthogonal question to the package format. Just keep debian/ in VCS if that works.
Is there somebody working on the Wig&Pen format ? -- DONE as 2.0 format and things has moved to 3.0 format.
Current situation
At the time of dpkg 1.14.17 release, 3.0 format was included and Bugs: 4588 et. al. was closed.