Re: [PATCH v2 08/23] checkout: fix bug with --to and relative HEAD

On Fri, Jul 3, 2015 at 10:45 PM, Duy Nguyen [off-list ref] wrote:

On Sat, Jul 4, 2015 at 7:17 AM, Eric Sunshine [off-list ref] wrote:

quoted

Given "git checkout --to <path> HEAD~1", the new worktree's HEAD should
begin life at the current branch's HEAD~1, however, it actually ends up
at HEAD~2. The happens because:

    1. git-checkout resolves HEAD~1

    2. to satisfy is_git_directory, prepare_linked_worktree() creates a
       HEAD in the new worktree with the value of the resolved HEAD~1

    3. git-checkout re-invokes itself with the same arguments within the
       new worktree to populate the worktree

    4. the sub git-checkout resolves HEAD~1 relative to its own HEAD,
       which is the resolved HEAD~1 from the original invocation,
       resulting unexpectedly and incorrectly in HEAD~2 (relative to the
       original)

Fix this by unconditionally assigning the current worktree's HEAD as the
value of the new worktree's HEAD.

Good catch!

quoted

@@ -924,9 +925,11 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
         * value would do because this value will be ignored and
         * replaced at the next (real) checkout.
         */

This comment "any valid value would do.. will be ignored" is proved incorrect.

Yup, and I meant to update the comment but promptly forgot about it.
Thanks for the reminder.