git-svn and local only topic branch

Hi,

I'm using Git as a SVN frontend (via git-svn). Recently, I made a topic branch, I did some job on it and wish to "upload" my work (on the SVN). But, I do not want "pushing" all commits, I only want to create a single commit on the SVN, while keeping full commits on my Git repo. But I did not find how to do this.

Here my story. Let's call "upstream" the local branch connected to the SVN, the raw SVN mirror branch is remotes/upstream. Now, I create a branch "topic" from "upstream" and I do job:

o--o--o (upstream, remotes/upstream)
         \
          o--o--o--o (topic)

I want the following result:

o--o--o-------------- o (upstream, remotes/upstream)
         \             /
          o--o--o--o (topic)

So I did "git-merge "Merge" upstream topic". But, the merge action decided to do a fast-forward. It's not correct because I really don't want to "pollute" the SVN with all my commits.

So I rewinded and I did "git-merge --squash "Merge" upstream topic". This time, it seems to work as I obtained a single commit on upstream branch. But this commit does not have ancestry link with the topic branch. Here is it:

o--o--o--o (upstream, remotes/upstream)
         \
          o--o--o--o (topic)

Is there a way to do what I want?

On May 1, 2007, at 9:40 AM, Guilhem Bonnefille wrote:

    If you just want to make a commit to Subversion containing all the  
changes on your branch, then you should be able to do this:

git svn commit-diff upstream topic

    That will take the entire diff between upstream and your topic  
branch and make one commit to Subversion containing that diff.

-Adam

On 5/1/07, Adam Roben <aroben@apple.com> wrote:

Yes, I want to make a single commit on Subversion containing all the changes of my topic branch. But I also want to keep track of this "merge" in my local Git repo. So I want that the new commit on my upstream branch store an ancestry with both upstream and topic branches.

I fear that "commit-diff" will only produce a commit on SVN, that will be stored as a single and normal commit on my (local) upstream branch.

On Tuesday 2007, May 01, Guilhem Bonnefille wrote:

No. Subversion doesn't do merge tracking. What you're asking for would require that. While git-svn is good, it cannot give subversion abilities it doesn't have.

It's an easy trap to fall into because git makes it so easy that you can forget that not everyone else can do it.

Andy

Guilhem Bonnefille wrote:

I did something similar recently:

http://www.spinics.net/lists/git/msg29119.html

The secret is to do a squash merge (git merge --squash) and commit that as a single revision onto the branch you commit into svn.

1--2--3------------4 (upstream)
       \
        A--B--C--D   (topic)

As far as git's history is concerned, at this point you have a topic branch with a bunch of commits ABCD, and an upstream branch with a bunch of commits 1234. Revision 4 has the contents of ABCD but is not marked as a merge in git's revision history, which means git-svn won't be confused since it doesn't know how to follow merges.

Now you do git svn dcommit to commit revision 4, which shows up as one commit on the svn side. git-svn will delete your revision 4 and create a new one whose comment includes the svn revision ID, so you'll have:

1--2--3------------4' (upstream)
       \
        A--B--C--D    (topic)

Since git-svn will never look earlier than revision 4' to figure out which svn revision it should use as a basis for future svn commits, you can do whatever you want with the history up to revision 4'. In particular, you can use git's "grafts" feature to fake git into thinking that a merge actually took place.

Open .git/info/grafts in your favorite editor and add a line with three SHA-1 hashes:

hash-of-4' hash-of-3 hash-of-D

Now as far as git is concerned you have the history you want:

1--2--3------------4' (upstream)
       \          /
        A--B--C--D    (topic)

Subsequent merges on the git side, whether they're squashed or not, will know about the merge you've just done.

In his reply to my script, Junio correctly pointed out that all this fiddling really ought to be happening in git-svn itself; it ought to know that you've done a merge and should record that fact directly in the metadata for 4' rather than treating it as a single-parent commit. If you do the above a zillion times you'll end up with a huge grafts file which is not so clean. But as a stopgap measure, this does work adequately.

-Steve

On 5/2/07, Steven Grimm <koreth@midwinter.com> wrote:

Yes, it's seems just fine. Thanks for the tips.

I'm not aware with the internal Git's features. As grafts seems to be a quick hack, is it posible to imagine that, after git-svn rewrited 4 in 4', an other tool rewrites (completly) the commit to produce a 4" with 2 parents?