Re: could not detach HEAD error didn't identify the cause of the issue

[Jeff King <peff@peff.net>]

On Mon, Sep 14, 2009 at 12:14:24PM +1200, Ben Bradshaw wrote:

> I was asked to post this issue to the list, I've just had git tell me it
> can't detach HEAD which left me scratching mine as to the cause and fix.
> Turns out if I have local untracked files that the remote branch also
> has then this error will trigger. I have included my shell backlog
> (client data removed). In this example the site_map folder was present
> on master and I had a local, untracked copy.
> 
> git can obviosly detect this issue and stop my local copy getting in a
> bad state, but an error message such as "sites/all/modules/site_map/ is
> present in HEAD but is untracked locally, unable to apply changes" (or
> something to point the finger) would be much appreciated.

I couldn't reproduce it here; I get such a message.

  # set up forked repo, "another" exists only on master
  $ mkdir repo && cd repo
  $ git init
  $ echo content >file && git add file && git commit -m base
  $ echo content >another && git add another && git commit -m another
  $ git checkout -b other HEAD^
  $ echo changes >file && git commit -a -m changes

  # add untracked "another" here
  $ echo untracked >another

  # try rebase
  $ git rebase master
  First, rewinding head to replay your work on top of it...
  error: Untracked working tree file 'another' would be overwritten by merge.
  could not detach HEAD

  # try git pull --rebase, in case it hides the message
  $ git config branch.other.remote .
  $ git config branch.other.merge refs/heads/master
  $ git pull --rebase
  From .
   * branch            master     -> FETCH_HEAD
  First, rewinding head to replay your work on top of it...
  error: Untracked working tree file 'another' would be overwritten by merge.
  could not detach HEAD

I'll admit the "could not detach HEAD" message would probably be better as:

  rebase: unable to move HEAD to 'master', aborting rebase

or something similar.

What version of git are you using? What does my test case above produce
for you?

-Peff