git-debrebase: Merge: Make a todo about gbp not round tripping

[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(7)>.
For background, theory of operation,
and definitions see L<git-debrebase(5)>.

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

=head1 PRINCIPAL OPERATIONS

=over

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

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

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

Then, if any git-rebase options were supplied,
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.

The options for git-rebase must either start with C<-i>,
or be prececded by C<-->,
to distinguish them from options for git-debrebase.

It is hazardous to use plain git-rebase on a git-debrebase branch,
because git-rebase has a tendency to start the rebase
too far back in history,
and then drop important commits.
Soo L<git-debrebase(5)/ILLEGAL OPERATIONS>

=item git-debrebase status

Analyses the current branch,
both in terms of its contents,
and the refs which are relevant to git-debrebase,
and prints a human-readable summary.

Please do not attempt to parse the output;
it may be reformatted or reorganised in the future.
Instead,
use one of the L<UNDERLYING AND SUPPLEMENTARY OPERATIONS>
described below.

=item git-debrebase conclude

Finishes a git-debrebase session,
tidying up the branch and making it fast forward again.

Specifically: if the branch is unstitched,
launders and restitches it,
making a new pseudomerge.
Otherwise, it is an error,
unless --noop-ok.

=item git-debrebase quick

Unconditionally launders and restitches the branch,
consuming any ffq-prev
and making a new pseudomerge.

If the branch is already laundered and stitched, does nothing.

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

If the branch is unstitched,
stitches it,
consuming ffq-prev.

This is a good command to run before pushing to a git server.
You should consider using B<conclude> instead,
because that launders the branch too.

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

Stitches the branch,
consuming ffq-prev.

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

You should consider using B<prepush> or B<conclude> instead.

=item git-debrebase scrap

Throws away all the work since the branch was last stitched.
This is done by rewinding you to ffq-prev.

If you are in the middle of a git-rebase, will abort that too.

=item git-debrebase new-upstream <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 snag 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.

<new-version>
may be whole new Debian version, including revision,
or just the upstream part,
in which case -1 will be appended
to make the new Debian version.

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

=over

=item <upstream-commit-ish>

The new upstream branch (or commit-ish).
The default is to look for one of these tags, in this order:
U vU upstream/U;
where U is the new upstream version.
(This is the same algorithm as L<git-deborig(1)>.)

It is a snag 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.

=item git-debrebase make-patches [--quiet-would-amend]

Generate patches in debian/patches/
representing the changes made to upstream files.

It is not normally necessary to run this command explicitly.
When uploading to Debian,
dgit and git-debrebase
will cooperate to regenerate patches as necessary.
When working with pure git remotes,
the patches are not needed.

Normally git-debrebase make-patches will
require a laundered branch.
(A laundered branch does not contain any patches.)
But if there are already some patches made by
git-debrebase make-patches,
and all that has happened is that more
changes to upstream files have been committed,
running it again can add the missing patches.

If the patches implied by the current branch
are not a simple superset of those already in debian/patches,
make-patches will fail with exit status 7,
and an error message.
(The message can be suppress with --quiet-would-amend.)
If the problem is simply that
the existing patches were not made by git-debrebase,
using dgit quilt-fixup instead should succeed.

=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 snag 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.
If it is not specified,
the same algorithm is used as for git-debrebase new-upstream.

It is also a snag 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.

git-debrebase will try to look for the dgit archive view
of the most recent release,
and if it finds it will make a pseduomerge so that
your new git-debrebase view is appropriately fast forward.

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

It is a snag if the new branch looks like it will have diverged,
just as for a laundering/unstitching call to git-debrebase;
See L</Establish the current branch's ffq-prev>, below.

Note that it is dangerous not to know whether you are
dealing with a gbp patches-unapplied 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!

=item git-debrebase convert-from-dgit-view [<convert-options>] [upstream]

Converts any dgit-compatible git branch
corresponding to a (possibly hypothetical) 3.0 quilt dsc source package
into a git-debrebase-compatible branch.

This operation should not be used
if the branch is already in git-debrebase form.
Normally git-debrebase will refuse to continue in this case
(or silently do nothing if the global --noop-ok option is used).

Some representation of the original upstream source code will be needed.
If I<upstream> is supplied, that must be a suitable upstream commit.
By default,
git-debrebase will look first for git tags (as for new-upstream),
and then for orig tarballs which it will ask dgit to process.

The upstream source must be exactly right and
all the patches in debian/patches must be up to date.
Applying the patches from debian/patches to the upstream source
must result in exactly your HEAD.

The output is laundered and stitched.
The resulting history is not particularly pretty,
especially if orig tarball(s) were imported
to produce a synthetic upstream commit.

The available convert-options are as follows.
(These must come after convert-from-dgit-view.)

=over

=item --[no-]diagnose

Print additional error messages to help diagnose
failure to find an appropriate upstream.
--no-diagnose is the default.

=item --build-products-dir

Directory to look in for orig tarballs.
The default is the git config option
dgit.default.build-products-dir
or failing that, C<..>.
Passed on to dgit, if git-debrebase invokes dgit.

=item --[no-]origs

Whether to try to look for or use any orig tarballs.
--origs is the default.

=item --[no-]tags

Whether to try to look for or use any upstream git tags.
--tags is the default.

=item --always-convert-anyway

Perform the conversion operation,
producing unpleasant extra history,
even if the branch seems to be in git-debrebase form already.
This should not be done unless necessary,
and it should not be necessary.

=back

=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<snag-id>

Turns snag(s) with id <snag-id> into warnings.

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

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

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

=item --force

Turns all snags into warnings.
See the -f<snag-id> option.

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

=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 logic which automatically classifies
commits as anchors, pseudomerges, delta queue commits, etc.

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

=item --dgit=<program>

Run <program>, instead of dgit from PATH,
when invocation of dgit is necessary.
This is provided mostly for the benefit of the test suite.

=item -D

Requests (more) debugging.  May be repeated.

=item --experimntal-merge-resolution

Enable experimental code for handling general merges
(see L<git-debrebase(5)/General merges>).

This option may generate branch structures that
require the use of this same option by other people.
Also you may experience lossage of various kinds,
including false error messages,
references to nonexistent documentation,
being handed an incomprehensible pile of
multidimensional merge wreckage,
and/or possible mangling of your package's source code.

=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 snag 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)