Re: [boost] [git][multi_index] help merging from develop

Subject: Re: [boost] [git][multi_index] help merging from develop
From: Bjørn Roald (bjorn_at_[hidden])
Date: 2013-12-25 12:38:34

On 12/25/2013 03:34 PM, Edward Diener wrote:
> On 12/25/2013 7:26 AM, Bjørn Roald wrote:

>> In fact the first merge into master from develop after the SVN to Git
>> conversion is important to get right. If not things become confusing as
>> Git has no sensible common ancestor for the two branches, and what merge
>> does may surprise you.
>
> Then this should be very carefully documented somewhere on the Wiki
> pages where all Boost developers can easily find it.

agreed, I think it is.  See below.

> I find it mysterious that one cannot do for one's own submodule:
>
> git checkout master
> git merge develop
> git push
>
> so evidently there is much more to this as far as Boost and git is
> concerned.

Not anything other than the fact the master and develop branch as they 
come out of the conversion from SVN are not really set up as normal git 
branches would.  They are just two separate branches running parallel 
from the infancy of the library with no interconnections in the form of 
recorded merges forming some common parent.  Such a common parent is 
normally used by git merge to end the search in history for change sets 
that may apply to the merge.

So Git may need a bit of care and help from you the first time you merge 
after the conversion to find a sensible place to make such a common 
parent.  Then that is done git will likely do as you expect.

Just doing the canonical merge you describe above as the first time 
merge after conversion will likely work if the head of the develop 
branch and the head of the master branches are in sync.  If not I 
recommend to look in the history of develop for a better commit to do 
the first merge from.  See link below.

> Hopefully what needs to be done will be carefully explained
> somewhere for all of us git non-experts.

There is a section called "First post-svn conversion merge to master" in:

https://svn.boost.org/trac/boost/wiki/StartModMaint#Gettingreadytoworkonalibrary

Is that similar to what you have in mind?

-- 
Bjørn