[dgit.git] / git-debrebase.1.pod

=head1 NAME

git-debrebase - delta queue rebase tool for Debian packaging

=head1 SYNOPSYS

 git-debrebase [<options...>] [-- <git-rebase options...>]
 git-debrebase [<options...>] <operation> [<operation options...>

=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 see L<git-debrebase(5)>.

You should read this manpage in conjunction with
L<git-debrebase(5)/TERMINOLOGY>,
which defines many important terms used here.

=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.

It is a problem if the branch is not laundered.

=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
(a multi-component upstream, in dpkg-source terminology),
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,
except for the laundering.

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

=over

=item <upstream-commit-ish>

The new upstream branch (or commit-ish).
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-commit-ish>

Specifies that this is a multi-piece upstream.
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-commit-ish>
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-deborig(1)>,
L<git-archive(1)>, L<dgit(1)> and
L<gbp-import-orig(1)> may be able to help.

This subcommand has -v0 in its name because we are not yet sure
that its command line syntax is optimal.
We may want to introduce an incompatible replacement syntax
under the name C<new-upstream>.

=item git-debrebase convert-from-gbp [<upstream-commit-ish>]

Cnnverts a gbp patches-unapplied branch
(not a gbp pq patch queue branch)
into a git-debrebase interchange branch.

This is done by generating a new anchor merge,
converting the quilt patches as a delta queue,
and dropping the patches from the tree.

The upstream commit-ish should correspond to
the gbp upstream branch, if there is one.
It is a problem if it is not an ancestor of HEAD,
or if the history between the upstream and HEAD
contains commits which make changes to upstream files.

It is also a problem if the specified upstream
has a debian/ subdirectory.
This check exists to detect certain likely user errors,
but if this situation is true and expected,
forcing it is fine.

The result is a well-formed git-debrebase interchange branch.
The result is also fast-forward from the gbp branch.

Note that it is dangerous not to know whether you are
dealing with a gbp patches-unappled branch containing quilt patches,
or a git-debrebase interchange branch.
At worst,
using the wrong tool for the branch format might result in
a dropped patch queue!

=back

=head1 UNDERLYING AND SUPPLEMENTARY OPERATIONS

=over

=item git-debrebase breakwater

Prints the breakwater tip commitid.
If your HEAD branch is not fully laundered,
prints the tip of the so-far-laundered breakwater.

=item git-debrebase anchor

Prints the breakwater anchor commitid.

=item git-debrebase analyse

Walks the history of the current branch,
most recent commit first,
back until the most recent anchor,
printing the commit object id,
and commit type and info
(ie the semantics in the git-debrebase model)
for each commit.

=item git-debrebase record-ffq-prev

Establishes the current branch's ffq-prev,
as discussed in L</UNSTITCHING AND LAUNDERING>,
but does not launder the branch or move HEAD.

It is an error if the ffq-prev could not be recorded.
It is also an error if an ffq-prev has already been recorded,
unless --noop-ok.

=item git-debrebase launder-v0

Launders the branch without recording anything in ffq-prev.
Then prints some information about the current branch.
Do not use this operation;
it will be withdrawn soon.

=item git-debrebase convert-to-gbp

Converts a laundered branch into a
gbp patches-unapplied branch containing quilt patches.
The result is not fast forward from the interchange branch,
and any ffq-prev is deleted.

This is provided mostly for the test suite
and for unusual situations.
It should only be used with a care and 
with a proper understanding of the underlying theory.

Be sure to not accidentally treat the result as
a git-debrebase branch,
or you will drop all the patches!

=back

=head1 OPTIONS

This section documents the general options
to git-debrebase
(ie, the ones which immediately follow
git-debrebase
or
git debrebase
on the command line).
Individual operations may have their own options which are
docuented under each operation.

=over

=item -f<problem-id>

Turns problems with id <problem-id> into warnings.

Some troublesome things which git-debrebase encounters
are B<problem>s.
(The specific instances are discussed
in the text for the relvant operation.)

When a problem is detected,
a message is printed to stderr containing the problem id
(in the form C<-f<problem-idE<gt>>),
along with some prose.

If problems are detected, git-debrebase does not continue,
unless the relevant -f<problem-id> is specified,
or --force is specified.

=item --force

Turns all problems into warnings.
See the -f<problem-id> option.

Do not invoke git-debrebase --force in scripts and aliases;
instead, specify the particular -f<problem-id> for expected problems.

=item --noop-ok

Suppresses the error in
some situations where git-debrebase does nothing,
because there is nothing to do.

The specific instances are discussed
in the text for the relvant operation.

=item --anchor=<commit-ish>

Treats <commit-ish> as an anchor.
This overrides the usual automatic commit classification logic.

It also disables some coherency checks
which depend on metadata extracted from its commit message,
so
it is a problem if <commit-ish> is the anchor
for the previous upstream version in
git-debrebase new-upstream operations.

=item -D

Requests (more) debugging.  May be repeated.

=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 ffq-prev is not yet recorded,
git-debrebase checks that the current branch is ahead of relevant
remote tracking branches.
The relevant branches depend on
the current branch (and its
git configuration)
and are as follows:

=over

=item

The branch that git would merge from
(remote.<branch>.merge, remote.<branch>.remote);

=item

The branch git would push to, if different
(remote.<branch>.pushRemote etc.);

=item

For local dgit suite branches,
the corresponding tracking remote;

=item

If you are on C<master>,
remotes/dgit/dgit/sid.

=back

The apparently relevant 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.

In each case it is a problem if
the local HEAD is behind the checked remote,
or if local HEAD has diverged from it.
All the checks are done locally using the remote tracking refs:
git-debrebase does not fetch anything from anywhere.

If these checks pass,
or are forced,
git-debrebse then records the current tip as ffq-prev.

=head2 Examine the branch

git-debrebase
analyses 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 SEE ALSO

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