File _service:obs_scm:README.PACKAGING of Package qemu

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File _service:obs_scm:README.PACKAGING of Package qemu

# PACKAGING WORKFLOW(S)

The qemu package follows a special maintenance workflow in order to support
git based patching, including of submodules. Please use it in order to have
changes you make be acceptable to the package maintainers.

All the development happens at https://github.com/openSUSE/qemu. The relevant
branch is `factory`.

Any change to the package should be submitted in the form of a Pull Request
against such repository and branch.

The reminder of this document provides more details, explanations and examples
for both contributors and maintainers.

# FOR CONTRIBUTORS

## BACKPORTING AN UPSTREAM PATCH

For submitting a backport of an upstream patch, proceed as follows (a local
copy of the repository is of course necessary).

Identify the hash of the commit that needs backporting and do:

git cherry-pick -esx <commit_hash>

This way, the changelog will already contain the reference to the upstream
commit itself, and the appropriate "Signed-off-by:" tag.

If the backport is related to Bugzilla (or Jira, and/or CVEs, etc) entry, add a
reference to that, such as:

Resolves: bsc#123456

Or:

References: jsc#PED-1234

Or:

Resolves: bsc#7891011 (CVE-1234-5678)

Add it between the "(cherry picked from commit ...)" line and the "Signed-off-by:"
line that follows it.

An example of the end result, where Dario Faggioli (<dfaggioli@suse.com>) is
backporting upstream commit abe2c4bdb65e8dd in order to fix bug 1209546 from
bugzilla.opensuse.org is:

test-vmstate: fix bad GTree usage, use-after-free
    
    According to g_tree_foreach() documentation:
    "The tree may not be modified while iterating over it (you can't
    add/remove items)."
    
    [...]
    
    Get rid of the node removal within the tree traversal. Also
    check the trees have the same number of nodes before the actual
    diff.
    
    Fixes: 9a85e4b8f6 ("migration: Support gtree migration")
    Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1518
    Signed-off-by: Marc-Andr303251 Lureau <marcandre.lureau@redhat.com>
    Signed-off-by: Eric Auger <eric.auger@redhat.com>
    Reported-by: Richard W.M. Jones <rjones@redhat.com>
    Tested-by: Richard W.M. Jones <rjones@redhat.com>
    Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
    Reviewed-by: Daniel P. Berrang303251 <berrange@redhat.com>
    Reviewed-by: Juan Quintela <quintela@redhat.com>
    Signed-off-by: Juan Quintela <quintela@redhat.com>
    (cherry picked from commit abe2c4bdb65e8dd9cb2f01c355baa394bf49a8af)
    Resolves: bsc#1209546
    Signed-off-by: Dario Faggioli <dfaggioli@suse.com>

Of course, all conflicts and issues should be resolved, before committing the
result/completing the cherry-picking.

At this point, the PR should be opened. As soon as that happens, some checks
will be run automatically and the maintainers of the QEMU package will review
and, eventually, merge or reject it.

PRs containing multiple commits are allowed. They are actually encouraged, if
the patches being backported are related and/or dependant among each others. It
must, however, always be the case that each upstream commit is cherry-picked
individually.

Note that there is no need to change any 'qemu.changes' file. That will, in
fact be handled by the package maintainers (and such RPM changelog entries will
be automatically generated out of the git commit messages).

## ADDING A PATCH NOT COMING FROM UPSTREAM

Downstream patches, i.e., patches that are not backports of upstream commits,
should be avoided as much as possible. The (largely!) recommended approach is
to submit the patch upstream and then, once it is accepted and committed,
backport it.

If that is not possible (for whatever reason), a pull request with a downstream
only patch can be opened. The procedure is almost identical to the one described
above for upstream backports. The main differences are:

1) Downstream only patch cannot be cherry-picked from upstream commits, of
   course. Therefore, the PR will consist of the commit(s) that introduces the
   patch.
 
2) There will be no "(cherry picked from commit ...") line in the changelog
   of a downstream only patch. On the other hand, the "Resolves:" or
   "Reference:" tag, that link the patch to the issue it's trying to solve,
   must be there, and the same is true for the "Signed-off-by:" tag
   indicating who is proposing adding it.

3) It is required that the subject of the commit starts with the [openSUSE] tag.

An example of a downstream only commit is:

[openSUSE] pc: q35: Bump max_cpus to 1024
    
    And use the new limit for machine version 7.1 too.
    Keep the old limit of 288 for machine versions 7.0 and earlier.
    
    Signed-off-by: Dario Faggioli <dfaggioli@suse.com>
    References: bsc#1202282, jsc#PED-2592
    Signed-off-by: Dario Faggioli <dfaggioli@suse.com>

## CHANGING THE PACKAGING FILES

Files that are necessary for building the RPM (like the spec file) or that
are part of the RPM and will be copied in the appropriate places in the
filesystem when it is installed are also part of the git repository. In fact,
they can be found in the `rpm/` directory.

Any addition, removal or change of and on any of those file should just be done
as a regular commit, and a pull request including such commit(s) should be
opened.

Commits to packaging files should be prefixed with both the [openSUSE] tag and
an [RPM] tag. An example can be this one:

[openSUSE][RPM] Add downstream packaging files
    
    Stash the "packaging files" in the QEMU repository, in the rpm/
    directory. During package build, they will be pulled out from there
    and used as appropriate.
    
    Signed-off-by: Dario Faggioli <dfaggioli@suse.com>

## ADDING A PATCH IN A SUBMODULE

For including a backport, or in general adding a patch, to a submodule, the
downstream git repository for the submodule must be checkedout at the location
where the submodule resides, in the main QEMU git repository.

For example, for including a downstream patch in the ipxe submodule, a local
copy of the repository https://github.com/openSUSE/qemu-ipxe.git is necessary.
After checking out the `factory` branch, add the patch there (cherry-picking
it from upstream, if it is a backport, and respecting all the tagging rules
explained in the previous sections).

At this point:
- the branch must be pushed;
- in the main (qemu) repository, a commit must be added and pushed, for making
  sure that the new patch is picked up.

Basically, the commit in the main repository is how the information that a
submodule as a new head is recorded.

The changelog of such commit shall include a reference to the subjects of all
the new commits in the various submodules. Unfortinately, there is not yet a
good way of achieving this automatically.

As last step, a pull request should be opened, as usual.

## REMOVING PATCHES

If a patch, or, in general, a commit, that is already part of the repository
must be removed, this must be done without rewriting the git history, i.e., with
a revert (and then a pull request with the revert should be opened).

# FOR MAINTAINERS

## REVIEWING AND ACCEPTING PRs

TODO

## COMMITTING CHANGES INTO FACTORY

TODO

## UPDATING THE BASE QEMU VERSION

TODO

# MANUAL AND AUTOMATED CHECKS

TODO

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