How can I get the parents of a merge commit in Git?

Question

Some Git commands take the parent as a revision; others (such as git revert), as a parent number. How can I get the parents for both cases?

I don’t want to use the graphical log command as that often requires scrolling down a long tree to find the second parent.

Answer 1

Simple git log <hash> called for a merge commit shows abbreviated hashes of its parents:

 $ git log -1 395f65d
 commit 395f65d438b13fb1fded88a330dc06c3b0951046
 Merge: 9901923 d28790d
 ...

git outputs parents according to their number: the first (leftmost) hash is for the first parent, and so on.

If all you want is just the hashes, the two equivalent choices are:

$ git log --pretty=%P -n 1 <commit>
$ git show -s --pretty=%P <commit>

git rev-list can also show the parents' hashes, though it will first list the hash for a commit:

$ git rev-list --parents -n 1 <commit>

If you want to examine the parents, you can refer to them directly with carats as <commit>^1 and <commit>^2, e.g.:

git show <commit>^1

This does generalize; for an octopus merge you can refer to the n^th parent as <commit>^n. You can refer to all parents with <commit>^@, though this doesn't work when a single commit is required. Additional suffixes can appear after the n^th parent syntax (e.g. <commit>^2^, <commit>^2^@), whereas they cannot after ^@ (<commit>^@^ isn't valid). For more on this syntax, read the rev-parse man page.