On Thu, Apr 12, 2018 at 12:53 PM, Johannes Schindelin
[off-list ref] wrote:

Hi Tiago,

On Thu, 12 Apr 2018, Tiago Botelho wrote:

quoted

On Thu, Apr 12, 2018 at 9:58 AM, Christian Couder
[off-list ref] wrote:

quoted

On Thu, Apr 12, 2018 at 9:49 AM, Harald Nordgren
[off-list ref] wrote:

quoted

I think it looks similar. But if I'm reading that thread correctly
then there was never a patch created, right?

(It is customary on this mailing list to reply after the sentences we
reply to. We don't "top post".)

On the GSoC idea pages (like https://git.github.io/SoC-2018-Ideas/) we
have been suggesting "Implement git bisect --first-parent" and there
are the following related links:

https://public-inbox.org/git/20150304053333.GA9584@peff.net/
https://public-inbox.org/git/4D3CDDF9.6080405@intel.com/

Tiago in Cc also tried at a recent London hackathon to implement it
and came up with the following:

https://github.com/tiagonbotelho/git/pull/1/files

I tried to help him by reworking his commit in the following branch:

https://github.com/chriscool/git/commits/myfirstparent

Thank you for the cc Christian, I’ve been quite busy and was not able
to work on the PR for quite some time.

I intended to pick it back up again next week. If it is ok with Harald
I would love to finish the PR that I started,
since it is quite close to being finished (I think it was just specs
missing if I am not mistaken).

That looks promising. Just like I suggested to Harald in another reply
[*1*] on this thread, you probably want to use `int flags` instead, and
turn `find_all` into BISECT_FIND_ALL in a preparatory commit.

Also, you will definitely want to add a test. Again, my reply to Harald
[*1*] should give you a head start there... You will want to imitate the
test case I outlined there, maybe something like:

# A - B - C - F
#   \   \   /   \
#     D - E - G - H

[... 'setup' as in my mail to Harald ...]

test_expect_success '--first-parent' '
        write_script find-e.sh <<-\EOF &&
        case "$(git show --format=%s -s)" in
        B|C|F) ;; # first parent lineage: okay
        *) git show -s --oneline HEAD >unexpected;;
        esac
        # detect whether we are "before" or "after" E
        test ! -f E.t
        EOF

        git bisect start --first-parent HEAD A &&
        git bisect run ./find-e.sh >actual &&
        test_path_is_missing unexpected &&
        grep "$(git rev-parse F) is the first bad commit" actual
'

Also, Tiago, reading through your patch (as on chriscool/git; do you have
your own fork? That would make it much easier to collaborate with you by
offering PRs), it looks more straight-forward than editing the commit_list
after the fact and adding magic weights ;-)

Except for one thing. I wonder why `bisect_next_all()` does not set
revs.first_parent_only after calling `bisect_rev_setup()`? You would still
need the changes in `count_distance()`, as it performs its own commit
graph traversal, but there is no need to enumerate too many commits in the
first place, right?

Harald, maybe --merges-only can be implemented on top of --first-parent,
with the `int flags` change I suggested?

Ciao,
Johannes

Footnote *1*:
https://public-inbox.org/git/nycvar.QRO.7.76.6.1804121143120.65@ZVAVAG-6OXH6DA.rhebcr.pbec.zvpebfbsg.pbz/

Hi Johannes,

Thank you for the pointers!

I do have my own fork, you can see it here:
https://github.com/tiagonbotelho/git/pull/1/commits
which applies the changes Chris made to my first draft of the solution.

I still have to add him as co-author of that commit.

Cheers,
Tiago Botelho