How do I find the next commit in Git? (child/children of ref)

Question

To list all the commits, starting from the current one, and then its child, and so on - basically standard git log, but going the other way in time, use something like

git log --reverse --ancestry-path 894e8b4e93d8f3^..master

where 894e8b4e93d8f3 is the first commit you want to show.

The creator of Hudson (now Jenkins), Kohsuke Kawaguchi published (November 2013): kohsuke / git-children-of:

Given a commit, find immediate children of that commit.

#!/bin/bash -e
# given a commit, find immediate children of that commit.
for arg in "$@"; do
  for commit in $(git rev-parse $arg^0); do
    for child in $(git log --format='%H %P' --all | grep -F " $commit" | cut -f1 -d' '); do
      git describe $child
    done
  done
done

---

As illustrated by this thread, in a VCS based on history represented by a DAG (Directed Acyclic Graph), there is not "one parent" or "one child".

        C1 -> C2 -> C3
      /               \
A -> B                  E -> F
      \               /
        D1 -> D2 ----/

The ordering of commits is done by "topo-order" or "date-order" (see the GitPro book).

But since Git 1.6.0, you can list the children of a commit.

git rev-list --children
git log --children

---

Note: for parent commits, you have the same issue, with the suffix ^ to a revision parameter meaning the first parent of that commit object. ^<n> means the <n>th parent (i.e. rev^ is equivalent to rev^1).

If you are on branch foo and issue "git merge bar" then foo will be the first parent.
I.e.: The first parent is the branch you were on when you merged, and the second is the commit on the branch that you merged in.

I found:

git rev-list --ancestry-path commit1..commit2

Where I set commit1 as the current commit and commit2 to the current head. This returns me a list of all commits which build a path between commit1 and commit2.

The last line of the output is the child of commit1 (on the path to commit2).

I know what you mean. It's frustrating to have plentiful syntax for going to previous commits, but none to go to the next ones. In a complex history, the problem of "what is the next commit" becomes rather hard, but then in complex merging the same hardness emerges with 'previous' commits as well. In the simple case, inside a single branch with a linear history (even just locally for some limited number of commits) it would be nice and make sense to go forward and backward.

The real problem with this, however, is that the children commits are not referenced; it's a backwards-linked list only. Finding the child commit takes a search, which isn't too bad, but it is probably not something Git wants to put into the refspec logic.

At any rate, I came upon this question, because I simply want to step forward in the history one commit at a time, doing tests, and sometimes you have to step forward and not backward. Well, with some more thought I came up with this solution:

Pick a commit ahead of where you're at. This could probably be a branch head. If you're at branch~10, "git checkout branch~9", "git checkout branch~8" to get the next after that, "git checkout branch~7" and so on.

Decrementing the number should be really easy in a script if you need it. A lot easier than parsing the Git rev-list.