Re: Syncing Gnus and Emacs repositories

[David Kastrup <dak@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> Cc: emacs-devel@gnu.org
>> From: David Kastrup <dak@gnu.org>
>> Date: Sat, 16 Jun 2007 16:05:16 +0200
>> 
>> Anyway, could you spell out the details of the compromise you are
>> trying to reach?
>
> I would like to find a way for the development to continue without
> interfering with Richard's goals.

Shouldn't this be rather "Richard's concepts"?  The continuation of
development should hardly interfere with Richard's _goals_.

> Using the Unicode branch for development sounds like a good
> candidate for that; you didn't yet say anything that would
> invalidate it.

It did not really come up.  So let me comment on it now: the problem I
see with that idea is that after the unicode-2/trunk merge, there will
be lots of areas where people and their favorite private packages will
get exposure to the unicode-2 internals the first time, and there will
be lots of problems to shake out.  If the merge consisted of just such
differences as can be contributed to the changed representation of the
multibyte strings and buffers, shaking out the problems encountered in
the process will be much easier if the branch has been kept reasonably
clean of unrelated changes and developments.

Basically your approach sounds to me like "let us make unicode-2 our
new trunk and work around Richard in that manner".  But one can't hope
to have something like that work consistently, and so some additions
will happen to unicode-2, and some to the trunk, and there will be a
lot of merge mess in two directions for which I see little motivation
and which actually is quite painful in CVS.

There is something to be said for the decentralized Linux kernel
source code management system git: basically, everybody pieces
together his favorite patches and branches, and merging is something
which everybody can do or let alone at his own leisure in his own
repository.  Interesting functionality is circulated as "patch sets",
and if one's personal branch has repeated conflicts with patch sets
from different branches, one can automate the conflict resolution
since git also keeps track of previous conflict resolutions.  It is
also easy to back out change sets again, even after one has had
conflict resolution.  I'll append a manual page for one particular
tool of its toolset.  It really is interesting.

But at the moment, we are using CVS, and everybody's trunk is the
same, and managed on Savannah instead of locally.  And that will
influence how people will treat it and work with it.  Distributing new
development among trunk and multitty and hoping that Miles and
Handa-san will sort out the mess for "a few months" more is not really
efficient if there is no particular goal achieved by that.

It is dealing with a code management problem by technical means,
expedience and additional manual work.  With good tools, the
additional manual work becomes less, but with our current setup I
think it problematic enough not to shrug it off lightly.

Of course, engaging people in shouting matches is also not efficient
use of their time.  There will be a time when I stop tearing my hairs
out publically when it turns out that I am not able to get my point
across, anyway.

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum

GIT-RERERE(1)                                                    GIT-RERERE(1)

NAME
       git-rerere - Reuse recorded resolve

SYNOPSIS
       git-rerere.sp

DESCRIPTION
       In a workflow that employs relatively long lived topic branches, the
       developer sometimes needs to resolve the same conflict over and over
       again until the topic branches are done (either merged to the "release"
       branch, or sent out and accepted upstream)..sp This command helps this
       process by recording conflicted automerge results and corresponding
       hand-resolve results on the initial manual merge, and later by noticing
       the same automerge results and applying the previously recorded hand
       resolution..sp

       Note
       You need to create $GIT_DIR/rr-cache directory to enable this
       command..sp

DISCUSSION
       When your topic branch modifies overlapping area that your master
       branch (or upstream) touched since your topic branch forked from it,
       you may want to test it with the latest master, even before your topic
       branch is ready to be pushed upstream:.sp

                        o---*---o topic
                       /
              o---o---o---*---o---o master
       For such a test, you need to merge master and topic somehow. One way to
       do it is to pull master into the topic branch:.sp

                  $ git checkout topic
                  $ git pull . master

                        o---*---o---+ topic
                       /           /
              o---o---o---*---o---o master
       The commits marked with * touch the same area in the same file; you
       need to resolve the conflicts when creating the commit marked with +.
       Then you can test the result to make sure your work-in-progress still
       works with what is in the latest master..sp After this test merge,
       there are two ways to continue your work on the topic. The easiest is
       to build on top of the test merge commit +, and when your work in the
       topic branch is finally ready, pull the topic branch into master,
       and/or ask the upstream to pull from you. By that time, however, the
       master or the upstream might have been advanced since the test merge +,
       in which case the final commit graph would look like this:.sp

                  $ git checkout topic
                  $ git pull . master
                  $ ... work on both topic and master branches
                  $ git checkout master
                  $ git pull . topic

                        o---*---o---+---o---o topic
                       /           /         \
              o---o---o---*---o---o---o---o---+ master
       When your topic branch is long-lived, however, your topic branch would
       end up having many such "Merge from master" commits on it, which would
       unnecessarily clutter the development history. Readers of the Linux
       kernel mailing list may remember that Linus complained about such too
       frequent test merges when a subsystem maintainer asked to pull from a
       branch full of "useless merges"..sp As an alternative, to keep the
       topic branch clean of test merges, you could blow away the test merge,
       and keep building on top of the tip before the test merge:.sp

                  $ git checkout topic
                  $ git pull . master
                  $ git reset --hard HEAD^ ;# rewind the test merge
                  $ ... work on both topic and master branches
                  $ git checkout master
                  $ git pull . topic

                        o---*---o-------o---o topic
                       /                     \
              o---o---o---*---o---o---o---o---+ master
       This would leave only one merge commit when your topic branch is
       finally ready and merged into the master branch. This merge would
       require you to resolve the conflict, introduced by the commits marked
       with *. However, often this conflict is the same conflict you resolved
       when you created the test merge you blew away. git-rerere command helps
       you to resolve this final conflicted merge using the information from
       your earlier hand resolve..sp Running git-rerere command immediately
       after a conflicted automerge records the conflicted working tree files,
       with the usual conflict markers <<<<<<<, =======, and >>>>>>> in them.
       Later, after you are done resolving the conflicts, running git-rerere
       again records the resolved state of these files. Suppose you did this
       when you created the test merge of master into the topic branch..sp
       Next time, running git-rerere after seeing a conflicted automerge, if
       the conflict is the same as the earlier one recorded, it is noticed and
       a three-way merge between the earlier conflicted automerge, the earlier
       manual resolution, and the current conflicted automerge is performed by
       the command. If this three-way merge resolves cleanly, the result is
       written out to your working tree file, so you would not have to
       manually resolve it. Note that git-rerere leaves the index file alone,
       so you still need to do the final sanity checks with git diff (or git
       diff -c) and git update-index when you are satisfied..sp As a
       convenience measure, git-merge automatically invokes git-rerere when it
       exits with a failed automerge, which records it if it is a new
       conflict, or reuses the earlier hand resolve when it is not. git-commit
       also invokes git-rerere when recording a merge result. What this means
       is that you do not have to do anything special yourself (Note: you
       still have to create $GIT_DIR/rr-cache directory to enable this
       command)..sp In our example, when you did the test merge, the manual
       resolution is recorded, and it will be reused when you do the actual
       merge later with updated master and topic branch, as long as the
       earlier resolution is still applicable..sp The information git-rerere
       records is also used when running git-rebase. After blowing away the
       test merge and continuing development on the topic branch:.sp

                        o---*---o-------o---o topic
                       /
              o---o---o---*---o---o---o---o   master

                  $ git rebase master topic

                                            o---*---o-------o---o topic
                                           /
              o---o---o---*---o---o---o---o   master
       you could run git rebase master topic, to keep yourself up-to-date even
       before your topic is ready to be sent upstream. This would result in
       falling back to three-way merge, and it would conflict the same way the
       test merge you resolved earlier. git-rerere is run by git rebase to
       help you resolve this conflict..sp

AUTHOR
       Written by Junio C Hamano <junkio@cox.net>.sp

GIT
       Part of the git(7) suite.sp

                                  03/05/2007                     GIT-RERERE(1)