X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=dgit.git;a=blobdiff_plain;f=README.git-debrebase;h=9efdc1aca4056a60a50ae7bfd7d8ba455f18910b;hp=8dcb0df4d165b641d070c1b2c2bfd2be393e8e2f;hb=8538600c6a51f6b02d1db7f7171f05a9651a27e6;hpb=d0a2fee062d2c79e9019fdebd96796d8b3ad6d5f diff --git a/README.git-debrebase b/README.git-debrebase index 8dcb0df4..9efdc1ac 100644 --- a/README.git-debrebase +++ b/README.git-debrebase @@ -1,48 +1,22 @@ -From: Ian Jackson -To: Sean Whitton -Cc: debian-devel@lists.debian.org -Subject: Re: Feedback on 3.0 source format problems -Date: Fri, 6 Jan 2017 15:29:38 +0000 -Sean Whitton writes ("Re: Feedback on 3.0 source format problems"): -> Could you explain in general terms the difference between the -> interchange and packaging-only branches - -See modified diagram below. Are the annotations I have added (and the -name change) any help ? - -> Does the packaging-only branch contain debian/ alone? - -No, it also contains a complete unmodified copy of the upstream code. -(Except that if upstream had a debian/ directory, it is completely -replaced.) Perhaps this is the wrong name. Let's try -`merging-baseline' -For `3.0 (quilt)' the merging-baseline branch contains roughly what -you would get if you untarred the origs and the debian.tar.gz, and -then deleted all the patches without applying them. - -Not shown on the diagram is the commit `add patch queue to -debian/patches', which would be needed for `3.0 (quilt)'. This is -because the diagram is in terms of a sane source format, not `3.0 -(quilt)'. For use with quilty sources, there would be such a commit -(probably dgit-generated) on top of the actual upstream change -commits: +My preferred answer is that it is a constantly rebasing branch topped +with a series of pseudomerges to make it fast-forwarding. ------/--A!----/--B3!--%--/--> interchange view / / / with debian/ directory % % % all upstream changes applied / / / 3.0 (quilt) has debian/patches - / 2* 2* + / / 3* / / / - 2* 2 2 + 2* 2* 2 / / / - 1 1 1 `merging-baseline' branch + 1 1 1 `breakwater' branch, merging baseline / / / unmodified upstream code - ---p-----p--A----p--B--C--> plus debian/ (but no debian/patches) - / / / - --#-----#-------#-----> upstream - + ---p-----p--A----p--B--C plus debian/ (but no debian/patches) + / / / no ref refers to this: we + --#-----#-------#-----> upstream reconstruct its identity by + inspecting interchange branch Key: 1,2,3 commits touching upstream files only @@ -51,7 +25,7 @@ commits: # upstream releases -p- special merge, takes contents of debian/ from the - / previous `merging-baseline' commit and rest from upstream + / previous `breakwater' commit and rest from upstream -/- pseudomerge; contents are identical to / parent lower on diagram. @@ -69,10 +43,138 @@ commits: Rebase branch launderer turns each ! into an equivalent *. -Ian. --- -Ian Jackson These opinions are my own. +Looking from the tip of the interchange view, it is I think always +possible to classify these commits appropriately: pseudomerges are +fairly obvious (if all three trees are identical, we descend to the +parent with the most recent commit date), and the `p' special merge is +the only non-pseudo merge and has a special form. + +So it would be possible to write a `git-debrebase' tool which would +take (for example) B4, above, and be able to perform functions like: + + * Strip pseudomerges: Rewrite the current branch so it contains no + pseudomerges, turning ...B3 into ...p-A-1-2-B3. (This should + make a note, in your .git/ somewhere, of the original branch + tip so that it can be overwritten with a pseudomerge.) + + * Cleanup branch: Reorganise the current branch so that the debian/ + changes come first, turning -p-A-1-2-B3 into ...p-A-B-1-2-3. + + * New upstream rebase: Start rebasing onto a new upstream version, + turning ...#..p-A-B-1-2-3 into (...#..p-A-B-|...#'-)p'-1-2. This + would be a wrapper around git-rebase, which prepares p' and then + tries to rebase 1 2 onto p'. So if you ask for an interactive + rebase p' doesn't appear in your commit list. + + Note that the construction of p' cannot fail because p' simply + copies debian/ from B and and everything else from #'. (Rebasing A + and B is undesirable. We want the debian/ files to be non-rebasing + so we can `git log' and get the packaging history.) + + * Record pseudomerge. This is like "committing" your patch queue. + The LH parent is taken from the previously recorded tip. (We could + perhaps check that this is consistent with what we see in + debian/changelog, but that is not a sufficient check so the + recorded tip check is primary.) + +Maybe some of these operations should automatically edit +debian/changelog. + +The only thing that this can't easily do is permit nonlinear (ie, +merging) history on the `packaging-only' branch, because upstream +might contain debian/ files too, so it is not possible to distinguish +a merge of two `packaging-only' branches from the special merge `p'. +(Indeed I since upstream might copy debian/ from us, I think it is not +easy to reliably distinguish the two parents of a `p'. In the most +exciting edge case, upstream might `git merge' a previous instance of +our interchange view, but I think even then everything still works.) + +Sean Whitton writes ("Re: Feedback on 3.0 source format problems"): +> Does the [breakwater] branch contain debian/ alone? -If I emailed you from an address @fyvzl.net or @evade.org.uk, that is -a private address which bypasses my fierce spamfilter. +No, it also contains a complete unmodified copy of the upstream code. +(Except that if upstream had a debian/ directory, it is completely +replaced.) + +For `3.0 (quilt)' the breakwater branch contains roughly what you +would get if you untarred the origs and the debian.tar.gz, and then +deleted all the patches without applying them. + + +dgit import handling +-------------------- + +Consider a non-dgit NMU followed by a dgit NMU: + + + + interchange --/--B3!--%--/----D*--> + / / + % 4 + / 3 + / 2 + / 1 + 2* &_ + / /| \ + 1 0 00 =XBC% + / + / + --p--A breakwater + / + --#--------> upstream + + + Key: + + =XBC% dgit tarball import of .debian.tar.gz containing + Debian packaging including changes B C and patches + + 0 dgit tarball import of upstream tarball + 00 dgit tarball import of supplementary upstream tarball + &_ dgit nearly-breakwater import + &' git-debrebase converted import (upstream files only) + D' git-debrebase converted debian/ changes import + + * ** before and after HEAD + +Want to transform this into: + + I. No new upstream version (0 + 00 eq #) + + --/--B3!--%--/------D*-------------/--> + / / / + % 4 4** + / 3 3 + / 2 2 + / 1 1 + 2* &_ / + / /| \ / + 1 0 00 =XBC% / + / / + / / + --p--A-----B-----------------------C--D + / + --#-----------------------------------------> + + + II. New upstream (0 + 00 neq #) + + --/--B3!--%--/------D*-------------/--> + / / / + % 4 4** + / 3 3 + / 2 2 + / 1 1 + 2* &_ / + / /| \ / + 1 0 00 =XBC% / + / / + / / + --p--A-----B--------------------p--C--D + / / + --#----------------------- - - / - - -----> + / + &' + /| + 0 00