How can I tell if one commit is an ancestor of another commit (or vice-versa)?

Question

Git is a DAG of snapshots, with each node on the graph representing a commit. Each commit can have \'n\' parent commits.

Given any two commits, is there a single, co

Answer 1

The following shell script might do the trick:

if git rev-list $SHA1 | grep -q $SHA2 ; then echo "$SHA2 is ancestor of $SHA1"
elif git rev-list $SHA2 | grep -q $SHA1 ; then echo "$SHA1 is ancestor of $SHA2"
else echo "$SHA1 unrelated to $SHA2" ; fi

Or, to neatly wrap it up into a git alias:

git config --global alias.related '!function git_related() { if git rev-list $1 | grep -q $2 ; then echo "$2 is ancestor of $1" ; elif git rev-list $2 | grep -q $1 ; then echo "$1 is ancestor of $2" ; else echo "$1 unrelated to $2" ; fi } ; git_related $1 $2'