bypass pre-commit hook for merge commits

As mentioned in this related answer you could test for the existence of $GIT_DIR/MERGE_HEAD to detect a merge commit:

Here's what you do get:

• If you're using git commit --amend to amend a merge commit, the pre-commit hook is run as usual, but it can't really detect that this is happening. The new commit will be a merge, but you can't tell.

• If you're using regular old git commit to create a non-merge commit, the file MERGE_HEAD will not exist in the git directory, and you can tell that this is not going to create a merge commit.

• If you're using git commit to finish off a conflicted merge, the file MERGE_HEAD will exist, and you can tell that this is going to create a merge commit.

• If you're running git merge and it succeeds on its own, it makes a new commit without using the pre-commit hook, so you don't even get invoked here.

Hence, if you're willing to allow git commit --amend on merges to misfire, you can get close to what you want: just test for the existence of $GIT_DIR/MERGE_HEAD to see if this is a git commit that is finishing off a conflicted merge. (The use of $GIT_DIR is a trick to make this work even if the commands are run outside the git tree. Git sets $GIT_DIR so that in-hook git commands will work right.)

So I just found a command that I think i can use to detect the "merge_head"

 git rev-parse -q --verify MERGE_HEAD

If rev-parse returns a hash that means we are currently in a merge state. I can use that to bypass this logic. But will wait for some better advice from more experienced individuals.