Referencing the child of a commit in Git

Question

If you want to move the HEAD to the parent of the current HEAD, that\'s easy:

git reset --hard HEAD^

But is there

Answer 1

To just move HEAD (as asked - this doesn't update the index or working tree), use:

git reset --soft $(git child)

You'll need to use the configuration listed below.

Explanation

Based on @Michael's answer, I hacked up the child alias in my .gitconfig.

It works as expected in the default case, and is also versatile.

# Get the child commit of the current commit.
# Use $1 instead of 'HEAD' if given. Use $2 instead of curent branch if given.
child = "!bash -c 'git log --format=%H --reverse --ancestry-path ${1:-HEAD}..${2:\"$(git rev-parse --abbrev-ref HEAD)\"} | head -1' -"

It defaults to giving the child of HEAD (unless another commit-ish argument is given) by following the ancestry one step toward the tip of the current branch (unless another commit-ish is given as second argument).

Use %h instead of %H if you want the short hash form.

With a detached head, there is no branch, but getting the first child can still be achieved with this alias:

# For the current (or specified) commit-ish, get the all children, print the first child 
children = "!bash -c 'c=${1:-HEAD}; set -- $(git rev-list --all --not \"$c\"^@ --children | grep $(git rev-parse \"$c\") ); shift; echo $1' -"

Change the $1 to $* to print all the children