Why recently, git rebase -i squash results in detached head

Question

Why does git rebase -i with squashes recently result in a detached head? It used to to update my current branch with the result of the interactive rebase. How do I get interactive rebase to stop going to detached HEAD?

I've always used git rebase -i to squash my commits before I pull from a remote repository to simplify handling any merge conflicts from the git pull. Instead of having to resolve conflicts over potentially multiple of my commits, I will only have to resolve one commit.

Sample command I use

# git rebase -i <tip of public branch> <my latest commit>
git rebase -i 380647533da 82f5ee67bed

After editing the rebase interactive in vim:

pick 3ec7c211c49 version1
s 82f5ee67bed some significant refactoring

Output after editting and saving the commit:

[detached HEAD ea50304796c] version1
 Date: Thu Jun 6 17:04:36 2019 -0400
 14 files changed, 213 insertions(+), 52 deletions(-)
 create mode 100644     some file
 create mode 100644     some file
 create mode 100644     some file
Successfully rebased and updated detached HEAD.

This differs from similar post git rebase -i develop HEAD leads to Detached Head because the asker wants to know HOW to resolve the issue for that ONE instance. the answer is git checkout -b branchName. In this question, I want to know WHY it started happening recently to me and HOW to resolve it for all FUTURE instances.

This differs from the similar post git rebase -i with squash cannot detach HEAD because the error message there is could not detach HEAD

Maya

Answer 1

The syntax guide for git rebase shows:

git rebase [-i | --interactive] [<options>] [--exec ] [--onto <newbase>] [<upstream> [<branch>]] git rebase [-i | --interactive] [<options>] [--exec <cmd>] [--onto <newbase>] --root [<branch>] git rebase --continue | --skip | --abort | --quit | --edit-todo | --show-current-patch

so your command:

git rebase -i 380647533da 82f5ee67bed

is providing 380647533da as the <upstream> and 82f5ee67bed as the <branch>.

The first paragraph in the description section says:

If <branch> is specified, git rebase will perform an automatic git checkout <branch> before doing anything else. Otherwise it remains on the current branch.

So, your git rebase is equivalent to:

git checkout 82f5ee67bed
git rebase 380647533da

The first command results in a detached HEAD. That detached HEAD remains that way when the rebase finishes.

Belomancy

Ah oh. I think I had a brain fart. I mixed up the parameters I usually use with 'git diff a b' and 'git rebase -i a'. I just started vacation. I'll try again when I get back and let you know. – Maya

Just got back from vacation and tried it out. For some reason, that day I started using git rebase -i a b instead of just git rebase -i a – Maya

Answer 2

I was doing:

git rebase -i 380647533da 82f5ee67bed

When I should have been doing what I always do:

git rebase -i 380647533da

Maya