What is the git-cherry equivalent for a single missing commit?

Question

How do I check if a single commit has already been applied to a specific branch?

Using the documentation of git-cherry as an example:

       $ git log --graph --oneline --decorate --boundary origin/master...topic
       * 7654321 (origin/master) upstream tip commit
       [... snip some other commits ...]
       * cccc111 cherry-pick of C
       * aaaa111 cherry-pick of A
       [... snip a lot more that has happened ...]
       | * cccc000 (topic) commit C
       | * bbbb000 commit B
       | * aaaa000 commit A
       |/
       o 1234567 branch point

       $ git cherry origin/master topic
       - cccc000... commit C
       + bbbb000... commit B
       - aaaa000... commit A

How would I know that cccc000 has the same content as - cccc111 without having to process the whole tree? Is this possible?

Notice that git-cherry relies on the patch content (diff) and this is key to the question.

Answer 1

git log has a --cherry-mark option which adds information on symmetric differences (a.k.a "3-dots operator" A...B)

Try running :

git log --oneline --graph --boundary --cherry-mark master...topic

You should see unique commits prefixed with + (or * when the --graph option is on), and commits present on both sides prefixed with =.

---

If you want to know how commits are matched : git patch-id computes the result used by cherry-pick / rebase.

git patch-id expects a patch (as produced by git show or git diff) on STDIN :

$ git show <commit-ish> | git patch-id
<hash for patch> <hash of input revision, if it can determine a revision>

For example : you can view the patch-ids of all individual commits in A...B :

git rev-list origin/master...forkpoint | while read sha1; do
    git show $sha1 | git patch-id
done

You can use this result in a script, to print more explicitly how commits are linked.