[PATCH] git-gui: give more advice when detaching HEAD

The current advice is a little sparse and dates back to d41b43e (git-gui: Refactor branch switch to support detached head, 2007-07-08). In the meantime, command-line git grew much more detailed advice for this situation, especially in 13be3e3 (Reword "detached HEAD" notification, 2010-01-29).

Let's use that more detailed advice here.

Signed-off-by: Jeff King <peff@peff.net>
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I recently helped somebody who had detached HEAD via git-gui, made a
bunch of commits, switched to another branch, and then became confused
about where his work went.

After working through what happened with him, I think this is one place where we could have prevented the problem. And given that we saw the need for more advice in the CLI, I think this change is a no-brainer.

I also think we could have saved him by doing one or more of:

  1. Give some indication or warning during commit that you're in a
     detached state. The CLI template says "You are not on any branch"
     when editing the commit message, and mentions "detached HEAD" as
     the branch in the post-commit summary. As far as I can tell,
     git-gui says nothing at all.

  2. When leaving the detached state, notice that we have commits not
     contained in any other ref and pop up an "are you sure you want to
     lose these commits" dialog, with an option to create a branch. This
     is something we considered and rejected for the CLI, but I wonder
     if it makes more sense for git-gui.

  3. Make it easier to create a new branch from the checkout dialog.
     Obviously I can go to "Branch->Create" and make a new branch from a
     remote one. But if my mental model is "Checkout", then I pick a
     remote branch, we may want to present the user with the decision
     _then_ about detaching or creating. Something as simple as a "make
     local branch from remote" checkbox would help. Or perhaps the
     "you're going to a detached HEAD" dialog should actually have a
     button to create a local branch right then and there instead. I
     dunno.

All of those things are too far beyond my scope of caring about git-gui and wanting to write tcl to actually implement myself. But I thought I would share them as thoughts that came from a real confused-user interaction. Feel free to ignore.

 lib/checkout_op.tcl |   13 ++++++++++---
 1 files changed, 10 insertions(+), 3 deletions(-)