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

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)?

   git log --ancestry-path $TOPIC..seen

doesn't work, because that excludes $TOPIC. (It does get me the merge of $TOPIC into seen, as well as all merges into seen following that merge, which I want, but it's missing the topic itself.)

  git log --ancestry-path $BASE_OF_TOPIC..seen

usually doesn't work, because $BASE_OF_TOPIC is usually a commit from "main" or "master", and this results in pulling in hundreds of commits from unrelated topics that also happen to be based on a version of "main" or "master" at or after $BASE_OF_TOPIC.

Is there some magic that does what I want, or is this just not possible currently?

Thanks, Elijah

[1] https://lore.kernel.org/git/CABPp-BHARfYcsEM7Daeb7+vYxeB9Awo8=qbrOMXG6BQ0gX1RiA@mail.gmail.com/

Elijah Newren <newren@gmail.com> writes:

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?

On 7/21/2022 11:37 AM, Junio C Hamano wrote:

Have you tried 

  git log --graph --oneline --boundary --ancestry-path <A>...<B>

The triple dots show the symmetric diff, and the --boundary shows the possible merge-bases. The --ancestry-path option seems to trim the output significantly in the example I tried.

Thanks, -Stolee

On Thu, Jul 21, 2022 at 8:37 AM Junio C Hamano <gitster@pobox.com> wrote:

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

   git log --ancestry-path topic..seen

I only get N-Q, missing L & M.  If I run

   git log --ancestry-path main..seen

then I get D-Q, providing me with D-I and J-K that I don't want.

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.

An example, from git.git; 5b893f7d81 is a topic (ab/submodule-cleanup) with 12 commits, and ac0248bfba is some older version of 'next' . I want all 12 commits in that topic plus all commits that are both descendants of that tip and ancestors of that old version of 'next', which adds up to 36 commits. (Note that this includes the 12 commits in ab/submodule clean, 9 commits from gc/submodule-use-super-prefix since that happens to be a descendant of ab/submodule-cleanup, and about 15 merge commits from merging other topics into next, but does not include those other 15 topics.) If I run (notice the "11" instead of "12"):

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

it reports 35 commits -- it's just missing the first commit from the topic. If I change "11" to "12" to try to get that first commit too:

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

then it reports 228 commits, 192 of which I don't want.

On 7/21/22 3:34 PM, Elijah Newren wrote:

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.

If you add --boundary, you should get that last commit as you want.

Thanks, -Stolee

On Fri, Jul 22, 2022 at 4:06 AM Derrick Stolee <derrickstolee@github.com> wrote:

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.