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Subject: Re: [OMPI devel] RFC: OMPI git mirror on
From: Jeff Squyres (jsquyres) (jsquyres_at_[hidden])
Date: 2012-08-18 11:42:46

FWIW: Ralph, I think Mike is proposing that we use the built in github SVN functionality. I.E., you can use git or SVN - both can read or write to the same backend repo. Pretty clever of github, actually. See the github blog entry he referenced, if you care.

But I agree: although dvcs are very nice and have many upsides, this would be a large change and there are downsides, too. Would definitely require more discussion, developer buy in, and planning, at a minimum.

Sent from my phone. No type good.

On Aug 18, 2012, at 11:28 AM, "Ralph Castain" <rhc_at_[hidden]<mailto:rhc_at_[hidden]>> wrote:

On Aug 18, 2012, at 8:21 AM, Mike Dubman <mike.ompi_at_[hidden]<mailto:mike.ompi_at_[hidden]>> wrote:

re item (5):

The current svn tree can be set as read-only and serve as a reference for old commit numbers.
It is rarery used anyway to search through historic commit numbers and can be done in read-only historic tree.

I use it a lot for old commits, but agree it is read-only for that purpose.

All other items can use svn interface of guthub and stay w/o any change.

Yeah, we've had experience with svn to git - no thanks!

It is pretty minor change (mostly mental) and pretty big gain

Guess we can agree to disagree - I found git to be awkward and a royal pain, especially when someone commits without doing a rebase (which happens a lot). No thanks.

On Sat, Aug 18, 2012 at 3:46 PM, Jeff Squyres <jsquyres_at_[hidden]<mailto:jsquyres_at_[hidden]>> wrote:
On Aug 18, 2012, at 8:27 AM, Jeff Squyres wrote:

> That's pretty clever, actually (SVN and git effectively together in the same repo). Cool!
> However, migrating to git has all the same problems that I mentioned in the prior email to you. Is Mellanox volunteering to do all the work for conversion?

I guess I should clarify -- here's what I previously sent to Mike in an off-list email about converting our main SVN repo to something else (e.g., Mercurial or Git). #3 is probably moot if we entirely move to github, but it would be replaced with "migrate all existing users to github" (which is a fair amount of work, too).

We have *many* discussions a year or two ago about making Mercurial the primary repo, not SVN, and ultimately rejected it. There's many issues involved:

1. developer learning curve
 --> certainly not the biggest factor, but definitely a factor
 --> "rebase" would certainly be a big deal (so that people don't put back a million intermediate commits)

2. adapting all of OMPI's current scripting to use hg (or git)
 --> this is a fair amount of work

3. getting IU to host git instead of SVN
 --> they have a whole management system for SVN: users, permissions, etc. No such thing exists for git.

4. integrating Trac with git. Or migrating to a whole new bug tracker that supports git.
 --> this is an entire conversation in itself. Note that everyone hates bugzilla.

5. re-writing the SVN history to find all references to "rXXX" in commit messages and replace them with the relevant hg (git) unique commit hash
 --> someone would have to figure out how to script that

So conversion would be a significant amount of work. Instead, we opted for our current modes of operation, which seem to be working well enough:

- use the hg+svn or git+svn combo mechanisms to do actual development in hg/git and then push back up to svn when done
- provide hg (and now git) official mirrors so that people can branch/clone from there, and then provide patches to commit when done with development

In short -- I agree with you: moving to 100% hg/git would be nice. But it would be a lot of work that no one was willing to spend the time to do.

Jeff Squyres
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