=head1 NAME

git-debrebase - delta queue rebase tool for Debian packaging

=head1 INTRODUCTION

git-debrebase is a tool for representing in git,
and manpulating,
Debian packages based on upstream source code.

This is the command line reference.
Please read the tutorial
L<dgit-maint-debrebase(5)>.

For background, theory of operation,
and definitions of the terms used here,
see L<git-debrebase(5)>.

=head1 PRINCIPAL OPERATIONS

=over

=item git-debrebase [-- <git-rebase options...>]

Unstitches and launders the branch.
(See L</UNSTITCHING AND LAUNDERING> below.)

Then optionally edits the Debian delta queue,
using git-rebase, by running

    git rebase <git-rebase options> <breakwater-tip>

Do not pass a base branch argument:
git-debrebase will supply that.
Do not use --onto, or --fork-point.
Useful git-rebase options include -i and --autosquash.

If git-rebase stops for any reason,
you may git-rebase --abort, --continue, or --skip, as usual.
If you abort the git-rebase,
the branch will still have been laundered,
but everything in the rebase will be undone.

=item git-debrebase stitch [--prose=<for commit message>]

Stitch the branch,
consuming ffq-prev.

If there is no ffq-prev, it is an error, unless --noop-ok.

=item git-debrebase new-upstream-v0 <new-version> [<upstream-details>...]

Rebases the delta queue
onto a new upstream version.  In detail:

Firstly, checks that the proposed rebase seems to make sense:
It is a problem unless the new upstream(s)
are fast forward from the previous upstream(s)
as found in the current breakwater anchor.
And, in the case of a multi-piece upstream,
if the pieces are not in the same order, with the same names.

If all seems well, unstitches and launders the branch.

Then,
generates
(in a private working area)
a new anchor merge commit,
on top of the breakwater tip,
and on top of that a commit to
update the version number in debian/changelog.

Finally,
starts a git-rebase
of the delta queue onto these new commits.

That git-rebase may complete successfully,
or it may require your assistance,
just like a normal git-rebase.

If you git-rebase --abort,
the whole new upstream operation is aborted,
but the laundering will still have been done.

The <upstream-details> are, optionally, in order:

=over

=item <upstream-commitish>

The new upstream branch (or commitish).
Default is C<upstream>.

It is a problem if the upstream contains a debian/ directory;
if forced to proceed,
git-debrebase will disregard the upstream's debian/ and
take (only) the packaging from the current breakwater.

=item <piece-name> <piece-upstream-commitish>

Specifies that this is a multi-piece upstream.
(A multi-component upstream, in dpkg-source terminology.)
May be repeated.

When such a pair is specified,
git-debrebase will first combine the pieces of the upstream
together,
and then use the result as the combined new upstream.

For each <piece-name>,
the tree of the <piece-upstream-commitish>
becomes the subdirectory <piece-name>
in the combined new upstream
(supplanting any subdirectory that might be there in
the main upstream branch).

<piece-name> has a restricted syntax:
it may contain only ASCII alphanumerics and hyphens.

The combined upstream is itself recorded as a commit,
with each of the upstream pieces' commits as parents.
The combined commit contains an annotation
to allow a future git-debrebase new upstream operation
to make the coherency checks described above.

=item <git-rebase options>

These will be passed to git rebase.

If the upstream rebase is troublesome, -i may be helpful.
As with plain git-debrebase,
do not specify a base, or --onto, or --fork-point.

=back

If you are planning to generate a .dsc,
you will also need to have, or generate,
actual orig tarball(s),
which must be identical to the rev-spec(s)
passed to git-debrebase.
git-debrebase does not concern itself with source packages
so neither helps with this, nor checks it.
L<git-archive(1)>, L<dgit(1)> and L<gbp(1)> may be able to help.

=back

=head1 UNSTITCHING AND LAUNDERING

Several operations unstitch and launder the branch first.
In detail this means:

=head2 Establish the current branch's ffq-prev

If it is not yet recorded, we
check that the current branch is ahead of relevant
remote tracking branches.

The remote tracking branches checked by default are
obtained from the git config.
In each case it is a problem if we are behind the checked remote,
or if we have diverged from it.
All the checks are local:
git-debrebase does not fetch anything from anywhere.

We check the branch we would merge from
(remote.<branch>.merge, remote.<branch>.remote)
and the branch we would push to
(remote.<branch>.pushRemote etc.).
For local dgit suite branches
we check the corresponding tracking remote.
If we are on C<master>, we check remotes/dgit/dgit/sid.
The resulting ref names to check are filtered through
branch.<branch>.ffq-ffrefs,
which is a semicolon-separated list of glob patterns,
each optionally preceded by !; first match wins.

If these checks pass,
or are forced,
we then record the current tip as ffq-prev.

=head2 Examine the branch

Analyse the current HEAD's history to find the anchor
in its breakwater,
and the most recent breakwater tip.

=head2 Rewrite the commits into laundered form

Mixed debian+upstream commits are split into two commits each.
Delta queue (upstream files) commits bubble to the top.
Pseudomerges,
and quilt patch additions,
are dropped.

This rewrite will always succeed, by construction.
The result is the laundered branch.

=head1 UNDERLYING AND SUPPLEMENTARY OPERATIONS

=over

=item git-debrebase breakwater

Prints the breakwater tip commitid.
Fails if your HEAD branch is not laundered.

=back

=head1 SEE ALSO

git-debrebase(1),
dgit-maint-rebase(7),
dgit(1)