Re: [boost] Git Modularization Review no vote heads-up

Subject: Re: [boost] Git Modularization Review no vote heads-up
From: Dave Abrahams (dave_at_[hidden])
Date: 2013-05-24 01:33:07

on Thu May 23 2013, Rene Rivera <grafikrobot-AT-gmail.com> wrote:

> On Thu, May 23, 2013 at 8:44 AM, Dave Abrahams <dave_at_[hidden]> wrote:
>
>>
>> on Thu May 23 2013, "Jürgen Hunold" <jhunold-AT-gmx.eu> wrote:
>>
>> > Dave wrote:
>>
>> I think that a one-to-one mapping like:
>> >
>> > repository build : common_branches
>> > {
>> >   submodule of "boost" : "tools/build";
>> >   content
>> >   {
>> >     "tools/build/" ;
>> >   }
>> >
>> > is the way to go now. If something goes wrong,
>>
>> It will, because we'd no longer be catching tools/jam throughout
>> history.  That will cause modularization to fail.
>>
>> > please put "tools/jam/" somewhere else.
>>
>> Yeah, that's not specific enough.  What is "somewhere else?"
>>
>
> branch = historical
> path = "jam/"

AFAICT, that doesn't work.  tools/jam (or its equivalent) has appeared
in many different SVN branches, including trunk.  You can't just squash
them all into one branch and come out with anything meaningful.

>> We could put it in the "engine" /v2/engine/ subdirectory of the build
>> repository, but that would be utterly inaccurate for older history.  We
>> can also have it move into /v2/engine from somewhere else (as it
>> actually does in SVN), but again, what is "somewhere else?"
>>
>> ...and—just checking—do you speak for the Boost.Build project, or is
>> Volodya likely to countermand your requests?
>>
>> > Btw. would
>> >
>> > repository build : common_branches
>> > {
>> >   submodule of "boost" : "tools/build";
>> >   content
>> >   {
>> >     "tools/build/v2" ;
>> >   }
>> >
>> > be the right way to move v2 one directory up?
>>
>> That would move the contents of v2 to the top level of the build repo,
>> but it would also drop all the commits that historically went directly
>> into tools/build/ (Boost.Build v1 mostly).  Like I said, we need
>> decisions about where *everything* that was in Boost.Build—throughout
>> history—belongs.
>
> Anything before v2 existed should go to:
>
> branch = historical
> path = "build/"

As before, you can't meaningfully squash everything into one branch.

> Or more descriptive..
>
> 1. Put anything that ever existed in the current build/v2/* files at the
> root of the new build repo.

Easy enough

> 2. Put anything else in some form of "historical" branch using the path
> from "boost-root/" 

? There's no "boost-root/" in SVN AFAIK

> as the path in the new repo. (I don't care that much about the actual
> branch names other than to tell that they are there only as history).
>
> But since I don't know git sufficiently.. I don't know if that's
> practically possible. Specifically I don't know if one can follow history
> back across branches. 

Branches in Git are merely (reference-counted) labels for commits, each
of which is the root of a history DAG.

When you merge branch A into branch B, you can follow history from B to
the last commit on A when it was merged, and thence to all of that
commit's ancestors.  If no further commits are made to A, it looks like
this:
                                
                              /--> A --> A~1 ...
  B --> B~1 --> B~2 ... B~N <
                              \--> B~(N+1) --> ...

If you mean something else by "follow history," I guess you'd better
explain.

> if it's not possible then I would say change #2 above to:
>
> 2. Put anything else at historical/jam, and historical/build in whatever
> branches you have now.

Are those (historical/jam and historical/build) supposed to be branch
names or paths?

-- 
Dave Abrahams