On July 1, 2019 3:48 PM, Bryan Turner wrote:
On Mon, Jul 1, 2019 at 12:35 PM Junio C Hamano <[email protected]> wrote:
>
> Eric Kulcyk <[email protected]> writes:
>
> [Overly long lines are not appreciated around here.]
>
> > We would like to track parent branches so that creating pull 
> > requests can automatically determine the correct branch to merge 
> > against.  I understand that this would require tracking more 
> > information than is currently available right now in git.  Also, it 
> > seems that if some cases, it is not possible to determine a parent 
> > branch, in which case it would just be empty/null.
>
> Do you mean by "parent branch" what people usually call "upstream 
> branch" (i.e. when that branch on the other side gains more commits 
> independent from what you have been working on, then you would want to 
> rebase your work on top of the updated state of that branch on the 
> other side) around here?

I suspect the question is in regards to "What branch did I create my local 
branch from?", especially given the pull request reference.

In other words, when I locally do:
git checkout --no-track -b bturner-some-bugfix origin/release/5.16

release/5.16 is the "parent branch" of my bugfix branch and, when I push my 
branch and try to open a pull request, release/5.16 is a _likely_ target for 
where I'd want to merge it. There may be a remote in the name, a la "origin" in 
my example, or it might be created on top of some other local branch. It's a 
common feature request for Bitbucket Server[1], for example, to automatically 
select the "right"
target branch for a new pull request based on the ancestry of the branch in 
question--except branches have no ancestry. (This sort of metadata could 
potentially offer some benefits for building commit graphs (referring to UI 
treatments for visualizing the DAG, rather than Git's "commit-graph" 
functionality), depending on how it was implemented, since it would make branch 
points more stable.)

Since branches are ephemeral names and have no intrinsic metadata of their own 
(unlike, say, annotated tags or commits), I suspect implementing something like 
this may be more complicated than it might initially appear, especially if said 
metadata needs to be communicated to remote repositories (which implies it 
might require changes to the wire protocol as well).

Best regards,
Bryan Turner

[1] https://jira.atlassian.com/browse/BSERV-7116

>
> Perhaps "git help glossary", look
> for "upstream branch" and start from there?  The entry mentions the 
> configuration variables used to keep track of that information, which 
> are described in "git help config", I think.
>
> > If I made a change to track the parent branch for each branch, would 
> > this feature be accepted/welcomed as part of git, even if it off by 
> > default?
>
> Regardless of what is being proposed, this is often not a very useful 
> question.  Something worth doing for yourself is worth doing whether 
> others also find it useful ;-)  And others usually do not have enough 
> information to judge if such a change is welcome until seeing it in a 
> bit more concrete form.

Was there not, at some point in recent history (2019), a discussion about 
storing extra arbitrary data associated with a branch or other objects? My 
thought for satisfying what Eric was originally proposing is to store the root 
commit associated with the original branch HEAD when checkout -b/branch was 
done to create the branch. Presumably another datum could store the branch that 
the branch HEAD was on, but that may not be unique - which is a root part of 
the problem with this request, although it might be something that the user 
could select/specify - not sure how - at branch creation. 

But aside from that both of the above are transient relative to the new branch 
and by the time you wanted to create a Pull Request, the information you 
originally wanted could irrelevant - at least to git. If I was the product 
manager on this, I would suggest going to GitLab, GitHub, or BitBucket and 
asking for some augmented capability of branch creation, that stores the data 
for future Pull Request management - instead of doing this in core git because 
of the transient nature of the relationship between a branch and a commit.

My $0.02.
Randall

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