Re: Question: How to find the commits in the ancestry path of seen down to _and_ including a given topic?

[Elijah Newren <newren@gmail.com>]

On Fri, Jul 22, 2022 at 4:06 AM Derrick Stolee <derrickstolee@github.com> wrote:
>
> On 7/21/22 3:34 PM, Elijah Newren wrote:
> > On Thu, Jul 21, 2022 at 8:37 AM Junio C Hamano <gitster@pobox.com> wrote:
> >>
> >> Elijah Newren <newren@gmail.com> writes:
> >>
> >>> A simple question that I'm spinning out of [1]: How can I get `git
> >>> log` to show the commits in the ancestry path from seen, back to *and
> >>> including* a given topic (but not commits from unrelated topics)?
> >>
> >> Drawing of a sample history, please.
> >>
> >> I feel stupid asking this, but I do not think I even understand what
> >> the question is X-<.
> >>
> >> Commits that are ancestors of 'seen' and are descendants of the tip
> >> of the topic?
> >
> > What you said *plus* commits from the topic itself.  From this graph:
> >
> >     A---B---C---J---K <-- main
> >             |\       \
> >             | \       N---------------O---P---Q <-- seen
> >             |  \     /               /
> >             |   L---M  <-- topic    /
> >              \                     /
> >               D---E---F---G---H---I  <-- other_topic
> >
> > I want the commits L-Q.  If I run
>
> Here is the thing I misunderstood. "topic" is already in "seen", so
> a seen...topic won't work at all.
>
> This idea is complicated by the fact that you have a concrete idea
> of which commits are in "topic", but you really can't do that without
> a definition of what it's based on. $(git merge-base main topic)
> would get you C, but then there are multiple paths from Q to C that
> don't go through topic.
>
> You can pull out that "first" commit in topic with this:
>
>   git revlist -1 --reverse main..topic
>
> but it only works if topic is a linear branch off of a single point
> in the history of main.
>
> > The closest I seem to be able to get is
> >
> >    git log --ancestry-path topic~${commits_in_topic_minus_one}..seen
> >
> > which includes all commits I want except the first commit of the topic
> > branch.
>
> If you add --boundary, you should get that last commit as you want.

It is nice that there's a way to get at least the commits I want (and
which is more limited than "C..topic"), but unfortunately this adds 16
extraneous commits to the 36 I want:

    $ git log --oneline --ancestry-path --boundary
5b893f7d81~11..ac0248bfba | wc -l
    52

I guess what I really want is something like (made up syntax):

    git log --ancestry-path=${tip_of_topic} main..seen

and have that be translated as listing commits in main..seen which has
$tip_of_topic directly within its ancestry path somewhere along the
line (i.e. either (1) has $tip_of_topic as an ancestor, or (2) has
$tip_of_topic as a descendant, or (3) is $tip_of_topic).  Then I'd get
exactly the 36 commits I want.  It'd be backward compatible too, since
a plain `--ancestry-path` with no stuck argument could just default to
using the bottom commit(s) in the range, as it does now.