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Merging

Merging is the process of taking all Ubuntu changes made on top of one Debian version of a package, and re-doing them on top of a new Debian version of the package.

See the Ubuntu wiki for a more detailed workflow. This guide is intended to cover the majority of use cases.

There is a list of packages that have been changed in Debian, but not merged into Ubuntu.

Overview

We do merges using git-ubuntu. As such, the process in many ways follows that of a git rebase, where commits from one point are replayed on top of another point:

--- something 1.2 ----------------------------- something 1.3
     \                                           \
      -- Ubuntu changes a, b, c -- 1.2ubuntu1     -- Ubuntu changes a, b, c -- 1.3ubuntu1

At a more detailed level, there are other subtasks to be done, such as:

  • Splitting out large "omnibus" style commits into smaller logical units (one commit per logical unit).
  • Harmonising debian/changelog commits into two commits: a changelog merge and a reconstruction.

With this process, we keep the Ubuntu version of a package cleanly applied to the end of the latest Debian version, and make it easy to drop changes as they become redundant.

Process steps

Preliminary steps

Decide on a merge candidate

First, you need to check if a newer version is available from Debian. For this, we can use the rmadison tool:

rmadison [package]
rmadison -u debian [package]

Example:

$ rmadison at
 at | 3.1.13-1ubuntu1   | precise | source, amd64, armel, armhf, i386, powerpc
 at | 3.1.14-1ubuntu1   | trusty  | source, amd64, arm64, armhf, i386, powerpc, ppc64el
 at | 3.1.18-2ubuntu1   | xenial  | source, amd64, arm64, armhf, i386, powerpc, ppc64el, s390x
 at | 3.1.20-3.1ubuntu2 | bionic  | source, amd64, arm64, armhf, i386, ppc64el, s390x
 at | 3.1.20-3.1ubuntu2 | cosmic  | source, amd64, arm64, armhf, i386, ppc64el, s390x
 at | 3.1.20-3.1ubuntu2 | disco   | source, amd64, arm64, armhf, i386, ppc64el, s390x
$ rmadison -u debian at
at         | 3.1.13-2+deb7u1 | oldoldstable       | source, amd64, armel, armhf, i386, ia64, kfreebsd-amd64, kfreebsd-i386, mips, mipsel, powerpc, s390, s390x, sparc
at         | 3.1.16-1        | oldstable          | source, amd64, arm64, armel, armhf, i386, mips, mipsel, powerpc, ppc64el, s390x
at         | 3.1.16-1        | oldstable-kfreebsd | source, kfreebsd-amd64, kfreebsd-i386
at         | 3.1.20-3        | stable             | source, amd64, arm64, armel, armhf, i386, mips, mips64el, mipsel, ppc64el, s390x
at         | 3.1.23-1        | testing            | source, amd64, arm64, armel, armhf, i386, mips, mips64el, mipsel, ppc64el, s390x
at         | 3.1.23-1        | unstable           | source, amd64, arm64, armel, armhf, hurd-i386, i386, kfreebsd-amd64, kfreebsd-i386, mips, mips64el, mipsel, ppc64el, s390x
at         | 3.1.23-1        | unstable-debug     | source

You'll be merging from Debian unstable, which in this example is 3.1.23-1.

Check existing bug entries

Check for any low hanging fruit in the Debian or Ubuntu bug list that can be wrapped into this merge.

If there are bugs you'd like to fix, make a new SRU style commit at the end of the merge process and put them together in the same merge proposal. This process is described in the adding new changes section below.

Make a bug report for the merge

Most of the regular server team merges are pre-planned and therefore likely exist already at our merges schedule and as bugs.

But we also sometimes pick up other merges from merge-o-matic, our weekly Merge Opportunities Report or just by getting aware due to any other reason.

In the case of not yet having an obvious pre-create bug search if there is existing merge request bug entry in Launchpad. If you don't find one, create one to avoid duplicate efforts and to allow coordination.

To do so go to the package's Launchpad page:

https://bugs.launchpad.net/ubuntu/+source/[package]

From there, create a new bug report requesting a merge.

Example:

URL: https://bugs.launchpad.net/ubuntu/+source/at/+filebug
Summary: "Please merge 3.1.23-1 into disco"
Description: "tracking bug"

result: https://bugs.launchpad.net/ubuntu/+source/at/+bug/1802914

Set the bug status to "in-progress" and assign it to yourself.

To let people only using m-o-m know go to the summary page (for example https://merges.ubuntu.com/universe.html) and if the package is listed there leave a comment linking to the bug. This way, others not studying the LP bugs will know more easily that there is already a bug filed for that merge. To do so go there and:

  • Click in the Comment column on the invisible text entry field
  • Leave a comment like "bug #123456" and press Enter
  • The page will update and link to your bug

Save the bug report number, because you'll be using it throughout the merge process.

Get the package repository

If not yet present, cloning the repository is the start of all further interaction. If instead the repository is already present, update it to ensure to have the newest content before any further action.

Clone the package repository

git ubuntu clone <package> [<package>-gu]

Example:

$ git ubuntu clone at at-gu

It's a good idea to append some git-ubuntu specific label (like -gu) to distinguish it from clones of Debian or upstream git repositories (which tend to want to clone as the same name).

Update the package repository

Since this is just git, the best way to update the git ubuntu based content as well as any other potentially added further remotes is to just update them all before going into the merge process.

$ git fetch --all

The merge process

Start a Git Ubuntu merge

From within the git source tree:

git ubuntu merge start pkg/ubuntu/devel

This will generate the following tags for you:

Tag Source
old/ubuntu ubuntu/devel
old/debian last import tag prior to old/ubuntu without ubuntu suffix in version
new/debian debian/sid

If git ubuntu merge start fails, do it manually.

Make a merge branch

Use the merge tracking bug and the current Ubuntu devel version it's going into (in the example of doing a merge below, the current Ubuntu devel was disco and the merge bug for the case was 1802914).

$ git checkout -b merge-lp1802914-disco

If there's no merge bug, the Debian package version you're merging onto can be used (for example merge-3.1.23-1-disco).

Sometimes you may notice a message like the following one when making the merge branch:

$ git checkout -b merge-augeas-mirespace-testing
Switched to a new branch 'merge-augeas-mirespace-testing'

WARNING: empty directories exist but are not tracked by git:

tests/root/etc/postfix
tests/root/etc/xinetd.d/arch

These will silently disappear on commit, causing extraneous
unintended changes. See: LP: #1687057.

These empty directories can cause the rich history to become lost when uploading them to the archive. Fortunately, a workaround exists.

Split commits

In this phase, you split out old-style commits that lumped multiple changes together.

Check if there are commits to split

$ git log --oneline

2af0cb7 (HEAD -> merge-3.1.20-6-disco, tag: reconstruct/3.1.20-3.1ubuntu2, tag: split/3.1.20-3.1ubuntu2) import patches-unapplied version 3.1.20-3.1ubuntu2 to ubuntu/disco-proposed
2a71755 (tag: pkg/import/3.1.20-5) Import patches-unapplied version 3.1.20-5 to debian/sid
9c3cf29 (tag: pkg/import/3.1.20-3.1) Import patches-unapplied version 3.1.20-3.1 to debian/sid
...

Get all commit hashes since old/debian and check the summary for what they changed, using:

git log --stat old/debian..

Example: (comes from merging heimdal package)

git log --stat old/debian..
commit 9fc91638b0a50392eb9f79d45d68bc5ac6cd6944 (HEAD ->
merge-7.8.git20221117.28daf24+dfsg-1-lunar)
Author: Michal Maloszewski <[email protected]>
Date:   Tue Jan 17 16:16:01 2023 +0100

    Changelog for 7.8.git20221117.28daf24+dfsg-1

 debian/changelog | 1 -
 1 file changed, 1 deletion(-)



commit e217fae2dc54a0a13e4ac5397ec7d3be527fa243
Author: Michal Maloszewski <[email protected]>
Date:   Tue Jan 17 16:13:49 2023 +0100

    update-maintainer

 debian/control | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)



commit 3c66d873330dd594d593d21870f4700b5e7fd153
Author: Michal Maloszewski <[email protected]>
Date:   Tue Jan 17 16:13:49 2023 +0100

    reconstruct-changelog

 debian/changelog | 10 ++++++++++
 1 file changed, 10 insertions(+)



commit 58b895f5ff6333b1a0956dd83e478542dc7a10d3
Author: Michal Maloszewski <[email protected]>
Date:   Tue Jan 17 16:13:46 2023 +0100

    merge-changelogs

 debian/changelog | 68
 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)

You can see that this command shows us the specific commit, as well as what was changed within the commit (i.e., how many files were changed and how many insertions and deletions are there).

If you see changelog with any other file(s) changing in a single commit, it's guaranteed that you'll need to split it. debian/changelog should only ever be changed in commits on its own, without touching any other file. You should still look over all commits just to make sure.

Another giveaway would be a commit named: Import patches-unapplied version 1.2.3ubuntu4 to ubuntu/cosmic-proposed, where it's applying from an Ubuntu source rather than a Debian one (in this case ubuntu4).

If there are no commits to split, simply add the split tag and move onto preparing the logical view.

Identify logical changes

The next step is to separate the changes into logical units. For the at package, this is trivial: just put the changelog change in one commit, and the control change in the other.

The second example, for nspr, is more instructive. Here we have 5 files changed, that need to be split out:

  • All changelog changes go to one commit called changelog.
  • Update maintainer (in debian/control) goes to one commit called update maintainers.
  • All other logically separable commits go into individual commits.

Look in debian/changelog:

nspr (2:4.18-1ubuntu1) bionic; urgency=medium

  * Resynchronize with Debian, remaining changes
    - rules: Enable Thumb2 build on armel, armhf.
    - d/p/fix_test_errcodes_for_runpath.patch: Fix testcases to handle
      zesty linker default changing to --enable-new-dtags for -rpath.

There are two logical changes, which we'll need to separate. Look at the changes in individual files to see which file changes should be logically grouped together.

Example:

$ git show d7ebe661 -- debian/rules

In this case, we have the following file changes to separate into logical units:

File(s) Logical unit
debian/rules Enable Thumb2 build on armel, armhf.
debian/patches/* Fix testcases to handle zesty linker default changing to --enable-new-dtags for -rpath.
debian/control Change maintainer
debian/changelog Changelog

Split out logical commits

Start a rebase at old/debian, and then reset to HEAD^ to bring back the changes as uncommitted changes.

  1. Start a rebase: git rebase -i old/debian
  2. Change the commit(s) you're going to split from pick to edit.
  3. Do a git reset to get your changes back: git reset HEAD^

Next, add the commits:

Logical unit:

$ git add debian/patches/*
$ git commit

Commit Message:

  * d/p/fix_test_errcodes_for_runpath.patch: Fix testcases to handle
    zesty linker default changing to --enable-new-dtags for -rpath.

Logical unit:

$ git add debian/rules
$ git commit

Commit Message:

  * d/rules: Enable Thumb2 build on armel, armhf.

Maintainers:

$ git commit -m "update maintainers" debian/control

Changelog:

$ git commit -m changelog debian/changelog

Finally, complete the rebase:

$ git rebase --continue

The result of this rebase should be a sequence of smaller commits, one per debian/changelog entry (with potentially additional commits for previously undocumented changes).

It should represent a broken-out history (viewable with git-log) for the latest Ubuntu version and no content differences to that Ubuntu version. This can be verified with git diff -p old/ubuntu.

Tag split

Note: Do this even if there were no commits to split.

$ git ubuntu tag --split

Purpose of logical tag

  • If we do this step, then we will have a distinct boundary between looking at the past (analysis of what is there already) and the actual work we want to perform (bringing the old Ubuntu delta forward).
  • By having a well-defined point, it is easier to do the future work, and also for a reviewer to start from the same point. The reviewer can very easily and almost completely automatically determine if the logical tag is correct.
  • The logical tag is the cleanest possible representation of a previous Ubuntu delta. By determining this representation, we make it as easy as possible to bring the delta forward.

Prepare the logical view

In this phase, we make a clean, "logical" view of the history. This history is cleaned up (but has the same delta), and only contains the actual changes that affect the package's behaviour.

We first start with a rebase from old/debian:

$ git rebase -i old/debian

Now we do some cleaning:

  • Delete imports, etc.
  • Delete any commit that only changes metadata like changelog, maintainer.
  • Possibly rearrange commits if it makes logical sense.

You should also squash these kinds of commits together:

  • Changes and reversions of those changes, since they resolve to a No-Op.
  • Multiple changes to the same patch file, since they should be a logical unit.

To squash a commit, move its line underneath the one you want it to become part of, and then change it from pick to fixup.

Check the result

At the end of the "squash and clean" phase, the only delta you should see from the split tag is:

$ git diff --stat split/6.8-0ubuntu2 
 debian/changelog | 31 -------------------------------
 debian/control   |  3 +--
 2 files changed, 1 insertion(+), 33 deletions(-)

Only changelog and control were changed, which is what we want.

Create logical tag

What is the logical tag? It is a representation of the Ubuntu delta present against a specific historical package version in Ubuntu.

$ git ubuntu tag --logical

This may fail with an error like: ERROR:HEAD is not a defined object in this git repository., in which case do it manually.

Rebase onto new Debian

$ git rebase -i --onto new/debian old/debian

Conflicts

If a conflict occurs, you must resolve it. We do so by modifying the conflicting commit during the rebase.

An example, merging logwatch 7.5.0-1:

$ git rebase -i --onto new/debian old/debian
...
CONFLICT (content): Merge conflict in debian/control
error: could not apply c0efd06... - Drop libsys-cpu-perl and libsys-meminfo-perl from Recommends to
...

Take a look at the conflict in debian/control:

    <<<<<<< HEAD
    Recommends: libdate-manip-perl, libsys-cpu-perl, libsys-meminfo-perl
    =======
    Recommends: libdate-manip-perl
    Suggests: fortune-mod, libsys-cpu-perl, libsys-meminfo-perl
    >>>>>>> c0efd06... - Drop libsys-cpu-perl and libsys-meminfo-perl from Recommends to

Upstream removed fortune-mod, and deleted the entire line since it was no longer needed. Resolve it to:

Recommends: libdate-manip-perl
Suggests: libsys-cpu-perl, libsys-meminfo-perl

Continue with the rebase:

$ git add debian/control
$ git rebase --continue

Corollaries

Mistake corrections are squashed.

Changes that fix mistakes made previous in the same delta are squashed against them. For example:

  • 2.3-4ubuntu1 was the previous merge.
  • 2.3-4ubuntu2 adjusted debian/rules to add a configure flag --build-beter
  • 2.3-4ubuntu3 fixed the typo in debian/rules to say --build-better instead.
  • When the logical tag is created, there will be only one commit relating to --build-better, which omits any mention of the typo.

Note:

If a mistake exists in the delta itself, then it is retained. For example, if 2.3-4ubuntu3 was never uploaded and the typo is still present in 2.3-4ubuntu2, then logical/2.3.-4ubuntu2 should contain a commit adding the configure flag with the typo still present.

Empty commits

If a commit becomes empty, it's because the change has already been applied upstream:

The previous cherry-pick is now empty, possibly due to conflict resolution.

In such a case, the commit can be dropped.

$ git rebase --abort
$ git rebase -i old/debian

Keep a copy of the redundant commit's commit message, then delete it in the rebase.

Sync request

If all the commits are empty, or you realised there are no logical changes, you're facing a sync request, not a merge. Refer to the sync guidelines to continue.

Check that the patches still apply cleanly

$ quilt push -a --fuzz=0

If quilt fails:

Quilt can fail at this point if the file being patched has changed significantly upstream. The most common reason is that the issue the patch addresses has since been fixed upstream.

For example:

$ quilt push -a --fuzz=0
...
Applying patch ssh-ignore-disconnected.patch
patching file scripts/services/sshd
Hunk #1 FAILED at 297.
1 out of 1 hunk FAILED -- rejects in file scripts/services/sshd
Patch ssh-ignore-disconnected.patch does not apply (enforce with -f)

If this patch fails because the changes in ssh-ignore-disconnected.patch are already applied upstream, you must remove this patch.

$ git log --oneline

1aed93f (HEAD -> ubuntu/devel)   * d/p/ssh-ignore-disconnected.patch: [sshd] ignore disconnected from user     USER (LP: 1644057)
7d9d752 - Drop libsys-cpu-perl and libsys-meminfo-perl from Recommends to   Suggests as they are in universe.

Removing 1aed93f will remove the patch.

  • Save the commit message from 1aed93f for later, including in the Drop Changes section of the new changelog entry.
  • git rebase -i 7d9d752 and delete commit 1aed93f.

Unapply patches before continuing

$ quilt pop -a

Adding new changes

Add any new changes you want to include with the merge. For instance, the new package version may fail to build from source (FTBFS) in Ubuntu due to new versions of specific libraries or runtimes.

Each logical change should be in its own commit to match the work done up to this point on splitting the logical changes.

Moreover, there is no need to add changelog entries for these changes manually. They will be generated from the commit messages with the merge finish process described below.

Finish the merge

$ git ubuntu merge finish pkg/ubuntu/devel

If this fails, do it manually.

Fix the changelog

Git Ubuntu attempts to put together a changelog entry, but it will likely have problems. Fix it up to make sure it follows the standards. See committing your changes for information about what it should look like.

Add dropped changes

If you dropped any changes (due to upstream fixes), you must note them in the changelog entry:

  * Drop Changes:
    - Foo: change to bar
      [Fixed in 1.2.3-4]

Format any new added changes

If you added any new changes, they should be in their own section in the changelog:

  * New Changes:
    - Bar: change to foo
    - Baz: adjust for Foo changes

Commit the changelog fix

$ git commit debian/changelog -m changelog

No changes to debian/changelog

The range old/ubuntu..logical/<version> should contain no changes to debian/changelog at all. We do not consider this part of the logical delta. So, any commits that contain only changes to debian/changelog should be dropped.

Tip

If you "diff" your final logical tag against the Ubuntu package it analyses, then the diff should be empty, except:

  1. All changes to debian/changelog:

    We deliberately exclude these from the logical tag, relying on commit messages instead.

  2. The change that update-maintainer introduced, and (rarely) similar changes like a change to Vcs-Git headers to point to an Ubuntu VCS instead.

    For the purposes of this workflow, these are not considered part of our “logical delta”, and instead are re-added at the end.

Tip

You can use execsnoop-bpfcc from the package bpfcc to find what debhelper scripts were called for a certain package. This is helpful for debugging what scripts were called, and what parameters were passed to them.

For example,

$ sudo apt install bpfcc-tools
$ sudo execsnoop-bpfcc -n multipath

Now in another shell run

$ sudo apt install --reinstall multipath-tools

In the original shell you should see something like

PCOMM            PID     PPID    RET ARGS
multipath-tools  13939   13931     0 /var/lib/dpkg/info/multipath-tools.prerm upgrade 0.9.4-5ubuntu3
multipath-tools  13951   13931     0 /var/lib/dpkg/info/multipath-tools.postrm upgrade 0.9.4-5ubuntu3
multipath-tools  13959   13956     0 /var/lib/dpkg/info/multipath-tools.postinst configure 0.9.4-5ubuntu3
multipathd       14009   1         0 /sbin/multipathd -d -s

A brief summary of this phase (cheat sheet)

  1. rmadison <package_name>
  2. rmadison -u debian <package_name>
  3. git ubuntu clone <package_name> <package_name>-gu
  4. cd <package_name>-gu
  5. git ubuntu merge start pkg/ubuntu/devel
  6. git checkout -b merge-<version_of_debian_unstable>-<current_ubuntu_devel_name>
  7. git log --stat old/debian..
  8. git ubuntu tag --split -> if nothing to split, type that command straight away
  9. git rebase -i old/debian
  10. Drop metadata changes and reorder/merge/split commits.
  11. git diff split/
  12. git ubuntu tag --logical
  13. git show logical/<version> -> check if the new tag exists
  14. git rebase -i --onto new/debian old/debian
  15. quilt push -a --fuzz=0
  16. quilt pop -a
  17. git ubuntu merge finish pkg/ubuntu/devel

Upload a PPA

Get orig tarball

Ubuntu doesn't know about the new tarball yet, so we must create it.

$ git ubuntu export-orig

If the upstream version does not yet exist in Ubuntu, that is, the new package from Debian also includes a new upstream version, you should add the --for-merge option:

$ git ubuntu export-orig --for-merge

If this fails, do it manually.

Build source package

$ dpkg-buildpackage \
 --build=source \
 --no-pre-clean \
 --no-check-builddeps \
 -sa \
 -v3.1.20-3.1ubuntu2

The switches are:

  • -sa = include orig tarball (required on a merge)
  • -vXYZ = include changelog since XYZ

Since our merge upload represents all changes that happened in Debian since our last merge plus anything added as part of the merge itself -v should usually point to the last published Ubuntu version. Here's an example:

  • Ubuntu merged as 1.3-1ubuntu1
  • Then Ubuntu had a fix in 1.3-1ubuntu2
  • But in the meantime Debian merged upstream as 1.4-1
  • And then added a fix in 1.4-2
  • New Ubuntu will be 1.4-2ubuntu1
  • -v should here be set to 1.3-1ubuntu2
    • Thereby the .changes file will include 1.4-1, 1.4-2, and 1.4-2ubuntu1
    • That represents all the changes that happened from the perspective of an Ubuntu user upgrading from 1.3-1ubuntu2 to 1.4-2ubuntu1`

If sponsoring a merge or any other upload for someone else, please remember the need to sign their upload with your key. See Sponsor a package for more information about that. Furthermore just like you the sponsor needs to know about e.g. setting -v right and using -sa when needed. If in doubt, coordinating with them will be helpful.

Push to your Launchpad repository

Now that the package is tested and builds successfully, it's time to push it to your Launchpad repository.

The easiest way is to run it like this:

git push your-lp-username

You'll get an error message and a suggestion for how to set upstream. For example:

$ git push kstenerud
fatal: The current branch merge-lp1802914-disco has no upstream branch.
To push the current branch and set the remote as upstream, use

    git push --set-upstream kstenerud merge-lp1802914-disco

Run the suggested command to push to your repository.

Push your lp tags

$ git push <your-git-remote> old/ubuntu old/debian new/debian reconstruct/<version> logical/<version> split/<version>

To ssh://git.launchpad.net/~kstenerud/ubuntu/+source/at
 * [new tag]         split/3.1.20-3.1ubuntu2 -> split/3.1.20-3.1ubuntu2
 * [new tag]         logical/3.1.20-3.1ubuntu2 -> logical/3.1.20-3.1ubuntu2
 * [new tag]         new/debian -> new/debian
 * [new tag]         old/debian -> old/debian
 * [new tag]         old/ubuntu -> old/ubuntu
 * [new tag]         reconstruct/3.1.20-3.1ubuntu2 -> reconstruct/3.1.20-3.1ubuntu2

Create a PPA

You'll need to have a PPA for reviewers to test.

Create a PPA repository

https://launchpad.net/~your-username/+activate-ppa

Give it a name that identifies the Ubuntu version, package name, and bug number, such as at-merge-lp1802914.

IMPORTANT:

Be sure to enable all architectures to check that it builds (click on Change details in the top right corner of the newly created PPA page).

Upload files

$ dput ppa:kstenerud/at-merge-lp1802914 ../at_3.1.23-1ubuntu1_source.changes

Wait for packages to be ready

Check the PPA page to see when packages are finished building: https://launchpad.net/~kstenerud/+archive/ubuntu/disco-at-merge-1802914

Also, look at the package contents to make sure they have actually been published: https://launchpad.net/~kstenerud/+archive/ubuntu/disco-at-merge-1802914/+packages

Test the new build

Test the following:

  1. Run package tests (if any)
  2. Upgrading from the previous version
  3. Installing the latest where nothing was installed before
  4. Other smoke tests

Test upgrading from the previous version

Example:

$ lxc launch ubuntu-daily:ubuntu/cosmic tester && lxc exec tester bash
$ apt update && apt dist-upgrade -y && apt install -y at

Note: Disco is not yet available at the time of writing, so we use Cosmic.

The test:

echo "echo xyz >test.txt" |at now + 1 minute && sleep 1m && cat test.txt && rm test.txt

Upgrade:

$ add-apt-repository -y ppa:kstenerud/at-merge-lp1802914

Note: Disco is not yet available at the time of writing, so we must modify the source list entry:

$ vi /etc/apt/sources.list.d/kstenerud-ubuntu-at-merge-lp1802914-cosmic.list
* change cosmic to disco

$ apt update && apt dist-upgrade -y

Test the upgraded version:

$ echo "echo abc >test.txt" | at now + 1 minute && sleep 1m && cat test.txt && rm test.txt

Test installing the latest from scratch

$ lxc launch ubuntu-daily:ubuntu/cosmic tester && lxc exec tester bash
$ add-apt-repository -y ppa:kstenerud/at-merge-lp1802914
$ apt update && apt dist-upgrade -y && apt install at
$ echo "echo abc >test.txt" | at now + 1 minute && sleep 1m && cat test.txt && rm test.txt

Other smoke tests

Submit Merge Proposal (MP)

NOTE:

Git branches with % in name don't work. Use something like _.

$ git ubuntu submit --target-branch debian/sid
Your merge proposal is now available at: https://code.launchpad.net/~kstenerud/ubuntu/+source/at/+git/at/+merge/358655
If it looks OK, please move it to the 'Needs Review' state.
  • Using a target branch of debian/sid may seem wrong, but is a workaround for LP: #1976112

If this fails, do it manually.

Update the merge proposal

  • Link the PPA
  • Add any other info (as a comment) that will help the reviewer to MP.

Example:

PPA: https://launchpad.net/~kstenerud/+archive/ubuntu/disco-at-merge-1802914

Basic test:

$ echo "echo abc >test.txt" | at now + 1 minute && sleep 1m && cat test.txt && rm test.txt

Package tests:

This package contains no tests.

Open the review

Change the MP status from "work in progress" to "needs review".

Follow the migration

Once the merge proposal goes through, you must follow the package to make sure it gets to its destination.

Package tests

The results from the latest package tests will be published for each Ubuntu release.

For example: http://autopkgtest.ubuntu.com/packages/o/openssh/focal/amd64

Proposed migration

The status of all packages will be available from the Ubuntu archive or one of its subdirectories. The top level directory is for the current dev release. Previous releases are in subdirectories.

Manual steps

Start a merge manually

Generate the merge branch

Create a branch to do the merge work in:

$ git checkout -b merge-lp1802914-disco

Create tags

Tag Source
old/ubuntu ubuntu/disco-devel
old/debian last import tag prior to old/ubuntu without ubuntu suffix in version
new/debian debian/sid

As per Debian releases, debian/sid always matches to Debian "unstable".

You can find the last import tag using git log | grep "tag: pkg/import" | grep -v ubuntu | head -1:

...
commit 9c3cf29c05c3fddd7359e71c978ff9a9a76e4404 (tag: pkg/import/3.1.20-3.1)

So, we create the following tags:

$ git tag old/ubuntu pkg/ubuntu/disco-devel
$ git tag old/debian 9c3cf29c05c3fddd7359e71c978ff9a9a76e4404
$ git tag new/debian pkg/debian/sid

Start a rebase

$ git rebase -i old/debian

Clear any history, up to and including the last Debian version

If the package hasn't been updated since the git repository structure changed, it will grab all changes throughout time rather than since the last Debian version. Just delete the older lines from the interactive rebase.

In this case, up to, and including import of 3.1.20-3.1.

Create reconstruct tag

$ git ubuntu tag --reconstruct

Next step: Split commits

Create logical tag manually

Use the version number of the last ubuntu change. So if there are 3.1.20-3.1ubuntu1 and 3.1.20-3.1ubuntu2, use 3.1.20-3.1ubuntu2.

$ git tag -a -m "Logical delta of 3.1.20-3.1ubuntu2" logical/3.1.20-3.1ubuntu2

Note:

Certain characters aren't allowed in git. For example, : should be replaced with %.

Next step: Rebase onto new Debian

Finish the merge manually

Merge the changelogs of old Ubuntu and new Debian:

$ git show new/debian:debian/changelog >/tmp/debnew.txt
$ git show old/ubuntu:debian/changelog >/tmp/ubuntuold.txt
$ merge-changelog /tmp/debnew.txt /tmp/ubuntuold.txt >debian/changelog
$ git commit -m "Merge changelogs" debian/changelog

Create a new changelog entry for the merge:

$ dch -i

Which creates, for example:

at (3.1.23-1ubuntu1) disco; urgency=medium

  * Merge with Debian unstable (LP: #1802914). Remaining changes:
    - Suggest an MTA rather than Recommending one.

 -- Karl Stenerud <[email protected]>  Mon, 12 Nov 2018 18:11:53 +0100

Commit the changelog:

$ git commit -m "changelog: Merge of 3.1.23-1" debian/changelog

Update maintainer:

$ update-maintainer
$ git commit -m "Update maintainer" debian/control

Next step: Fix the changelog

Get the orig tarball manually

$ git checkout -b pkg/importer/debian/pristine-tar
$ pristine-tar checkout at_3.1.23.orig.tar.gz
$ git checkout merge-3.1.23-1-disco

If git checkout also fails

$ git checkout merge-lp1802914-disco
$ cd /tmp
$ pull-debian-source at
$ mv at_3.1.23.orig.tar.gz{,.asc} ~/work/packages/ubuntu/
$ cd -

Next step: Check the source for errors

Submit merge proposal manually

$ git push kstenerud merge-lp1802914-disco

Then, create a MP manually in Launchpad, and save the URL.

Next step: Update the merge proposal

Known issues

Empty directories

We need to use a python script written by Robie Basak (@racb). Why is it a problem that we get empty directories?

Git's frontend doesn't let you add an empty directory. Usually the workaround is to create any necessary empty directory at build time, or failing that, to create a placeholder file like .empty and check that in.

Neither of these approaches work for git-ubuntu's importer in the general case. A source package can ship an empty directory by nature of the source package format. But the build system (i.e. debian/rules) in the source package expects the source exactly as packed. Just as some builds break if empty directories are missing, other builds might break if empty directories are not actually empty.

Internally, git supports empty directories just fine. Directories map to git tree objects. An empty tree object is the obvious way of representing an empty directory, and git seems to accept them if they are represented this way. It's just the git index and frontend that do not support them.

In git-ubuntu, we therefore import empty directories "correctly" and losslessly by using empty tree objects as necessary. However, when such a tree is checked out at the client end, the empty directories disappear as they pass through the index, and get lost. A subsequent commit made by a developer then gets created from the index, so does not include the empty directories even if they haven't been touched.

This becomes an issue if such a commit is subsequently presented back to git-ubuntu as rich history to be adopted against an upload. git-ubuntu finds that the upload (with empty directories) doesn't match the rich history commit (with missing empty directories).

This script restores the empty directories locally as a workaround. It takes a non-merge commit and examines its parent to discover which empty directories have been lost. It provides an equivalent replacement commit.

Run it with fix-head to replace HEAD with a commit that has empty directories restored.

Run it with fix-many and a parameter pointing to a base commit to run git-rebase to fix a set of commits.

Note that in both cases, the parent must have the empty directories in order for them to be copied down through the fixed-up commits. In the common case where this script is needed, you'll be starting from an "official" git-ubuntu import tag or branch, so this will be true in these cases. However, this does mean that you need to use fix-many all the way back to the first commit after such an "official" commit. If you have intermediary un-fixed commits and then try to apply fix-head to the end, then it won't work as the empty directories won't get copied forward.

Example of use:

git ubuntu clone apache2
cd apache2
git tag -f base
<add commits>
python3 emptydirfixup.py fix-many base
git ubuntu tag --upload

For an entire real case you can follow this workflow:

# get emptydirfxup script
wget -O ../emptydirfixup.py "https://git.launchpad.net/~racb/usd-importer/plain/wip/emptydirfixup.py?h=emptydirfixup"

# clone as usual
git ubuntu clone "${source_package}" "${source_package}-gu"
cd "${source_package}-gu/"

# make the merge branch (here you see the warning message)
git checkout "${last_remote}" -b "${branch_name}"

# tag the base and rebase on ubuntu/devel
git tag -f base
git checkout ubuntu/devel
git rebase base

# start the merge
git ubuntu merge -f start

#... Merge work as usual ...

# Workaround LP: #1939747
rm .git/hooks/pre-commit

# finish the merge
git ubuntu merge finish pkg/ubuntu/devel

#... Create MP as usual, get reviewed/approved, etc. ...

# Fix the empty dir set of commits
python3 ../emptydirfixup.py fix-many base

# Build the package
debuild -S $(git ubuntu push-for-upload)

# Uploading
git push pkg "upload/${version}"
dput ubuntu "${changes_file}"

#... Done! ...