vendor/illumos merges

[Mark Millard]

On 2021-Apr-24, at 03:44, Ulrich Spörlein <uqs at freebsd.org> wrote:

> On Fri, 2021-04-23 at 17:26:33 -0400, Mark Johnston wrote:
>> Hi,
>> 
>> Now that FreeBSD uses OpenZFS as the upstream for ZFS, vendor/illumos is
>> mostly unused.  However, we still use illumos as an upstream for CTF
>> tools and DTrace, though there haven't been any imports in a while.
>> 
>> illumos has put a lot of work into their CTF toolchain, and I'd like to
>> import that.  There are a couple of snags that I'd appreciate some
>> guidance on.
>> 
>> First, I believe I should delete now-unused ZFS code from the vendor
>> branch and merge the result to main.  I did this locally and got an
>> empty merge, which is what I'd expect.  Is there any problem with this?
> 
> Why would you record this empty merge? If you clean up vendor/foo, just do that but don't merge a no-op back into main (nothing changed, after all).
> 
>> Second, with Subversion we had both vendor/illumos and
>> vendor-sys/illumos, and now we just have the former, seemingly with
>> sys/* bits imported from vendor-sys.  Some of the upstream commits touch
>> both userspace and kernel bits, but the merge targets for these in
>> FreeBSD are different: cddl/contrib/opensolaris vs.
>> sys/cddl/contrib/opensolaris.  How should I merge into main in this
>> case?  I don't really see any options other than to split each offending
>> upstream commit into two parts, one for userspace and one for the
>> kernel, and merge them separately.
>> 
>> If it helps to look at the branch where I staged the upstream commits,
>> I've pushed it to vendor/illumos2 in https://github.com/markjdb/freebsd
>> .
> 
> Can you clarify why the merging of the two might be an issue? Note that unlike subversion, in git there's no "merge a certain subtree" handling

It might be an ambiguous terminology context for what is being
referenced, but there is :

# man git-subtree
GIT-SUBTREE(1)                                                  GIT-SUBTREE(1)






NAME
       git-subtree - Merge subtrees together and split repository into
       subtrees

SYNOPSIS
       git subtree add   -P <prefix> <commit>
       git subtree add   -P <prefix> <repository> <ref>
       git subtree pull  -P <prefix> <repository> <ref>
       git subtree push  -P <prefix> <repository> <ref>
       git subtree merge -P <prefix> <commit>
       git subtree split -P <prefix> [OPTIONS] [<commit>]

. . .

Its usage has tradeoffs from what I can tell reading about
it as an alternative to submodules.

There is also a not-predefined-in-git alternative:

https://github.com/ingydotnet/git-subrepo#readme

> , all that is recorded is a tree of some form and then a set of parents or ancestor commits. (git is a content tracker, not really a VCS :)
> 
> I was under the impression that userland and kernel imports/merges need to happen at the same time anyway, so I assume you would import all the bits under vendor/foo in 1 commit and then merge them in 1 commit into main. Is that not how it goes?


===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)