=head1 NAME

dgit-nmu-simple - tutorial for DDs wanting to NMU with git

=head1 INTRODUCTION AND SCOPE

This tutorial describes how a Debian Developer can do
a straightforward NMU
of a package in Debian, working (only) in git.

This document won't help you decide whether
an NMU is a good idea or
whether it be well received.
The Debian Developers' Reference has some
(sometimes questionable) guidance on this.

Conversely, you do not need to know anything
about the usual maintainer's git workflow.
If appropriate, you can work on many different packages,
making similar changes,
without worrying about the individual maintainers' git practices.

This tutorial only covers changes which
can sensibly be expressed as a
reasonably small number of linear commits
(whether to Debian packaging or to upstream files or both).

If you want to do a new upstream version,
you probably want to do as the maintainer would have done.
You'll need to find out what the maintainer's
git practices are
and 
consult the appropriate C<dgit-maint-*(7)> workflow tutorial,

=head1 SUMMARY

=over 4

    % dgit clone glibc bookworm
    % cd glibc
    % git am ~/glibc-security-fix.diff
    % dch --nmu "Apply upstream's fix for foo bug."
    % git add debian/changelog && git commit -m"NMU changelog entry"
    % dpkg-buildpackage -uc -b
    [ run your tests ]
    % dch -r && git add debian/changelog && git commit -m"Finalise NMU"
    % dgit -wgf sbuild -A -d trixie
    [ any final tests on generated .debs ]
    % dgit -wgf [--delayed=5] push-source bookworm
    [ enter your gnupg passphrase as prompted ]
    [ see that push and upload are successful ]
    [ prepare and email NMU diff (git-diff, git-format-patch) ]

=back

=head1 WHAT KIND OF CHANGES AND COMMITS TO MAKE

When preparing an NMU, the git commits you make on the dgit branch
should be simple linear series of commits with good commit messages.
The commit messages will be published in various ways,
including perhaps being used as the cover messages for
generated quilt patches.

Do not make merge commits.
Do not try to rebase to drop existing patches - if you need to revert a
change which is actually a Debian patch,
use git-revert.

If you need to modify a Debian patch,
make a new commit which fixes what needs fixing,
and explain in the commit message which patch it should be
squashed with
(perhaps by use of a commit message in C<git rebase --autosquash -i>
format).

(Of course if you have specific instructions from the maintainer,
you can follow those instead.
But the procedure in this tutorial is legitimate for any maintainer,
in the sense that it should generate an upload to which the
maintainer cannot reasonably object.)

=head1 PREPARING AND REVISING THE LOCAL BRANCH

The dgit/sid branch is
a normal local git branch tracking a (synthetic) upstream branch.
So you can freely rewrite any commits that you have made locally
and haven't pushed anywhere,
as normal,

The one thing that's weird is the "quilt fixup" commits
(that turn up if you do eg dgit sbuild).
If you're rebasing them at all, you can and should just drop them;
dgit will then regenerate them as needed.

All of this follows from one underlying fact:

dgit doesn't have invisible git state somewhere.
So if you rebase away the quilt fixup, and rework your branch,
your branch is still good because it looks just like it would do,
if you'd just made those commits straight off.
(NB git-debrebase B<does> have weird off-branch state.)

=head1 RELEVANT BRANCHES

dgit clone will put you on a branch like C<dgit/sid>.
There is a pseudo-remote called C<dgit> which also contains a branch
like C<dgit/sid>, so you do things like
C<git diff dgit/dgit/sid>
to see what changes you have made.

=head1 KEEPING YOUR WORKING TREE TIDY

Don't forget to C<git add> any new files you create.
Otherwise git clean
(which is requested with the C<-wgf> option in the recipe above)
will delete them.

Many package builds leave dirty git trees.
So, commit before building.
That way you can use C<git reset --hard>.

If you follow this approach
you don't need to care about the build dirtying the
tree.
It also means you don't care about the package clean target,
which is just as well because many package clean targets are broken.

=head1 OTHER GIT BRANCHES

The dgit git history
(visible in gitk and git log)
is not necessarily related to the maintainer's
or upstream's git history (if any).

If the maintainer has advertised a git repo with
Vcs-Git
dgit will set up a remote for it,
so you can do

=over 4

    % git fetch vcs-git

=back

You can cherry pick changes from there, for example. 
Note that the maintainer's git history may not be
suitable for use with dgit.
For example, it might be a patches-unapplied branch
or even contain only a debian/ directory.

=head1 UPLOADING TO DELAYED

You can use dgit's I<--delayed> option
to upload to the DELAYED queue.
However, you should read the warning about this option in dgit(1).

=head1 WHAT ABOUT GIT-DEBPUSH/TAG2UPLOAD?

Uploading with B<git-debpush> is not usually a good fit for NMUs because an
NMUer usually does not want to, or cannot, push to the maintainer's git
repository on B<salsa.debian.org>.

=head1 SEE ALSO

dgit(1), dgit(7), dgit-maint-*(7)
