Re: master^ is not a local branch -- huh?!?

On Fri, 29 Jan 2010, Junio C Hamano wrote:

We used to just say "topic is not a rev nor path" and failed when the user
said "git checkout topic".  And the magic kicks in when there is only one
"remotes/*/topic".

Because this cannot be any request other than to check out a local branch
"topic", and because there is no place more sensible than the "topic"
taken from the "origin" (as that is the sole place that has "topic"), it
dwims as a shorthand for "checkout -b topic origin/topic" and tells you
that it did so.

OK.  That is probably sensible.

I don't think any improvement on the detached head message should 
presume on this though.

And it might be a good idea to say explicitly that what happened is the 
creation of a detached HEAD, like in:

diff --git a/builtin-checkout.c b/builtin-checkout.c
index 5277817..c0a44d7 100644
--- a/builtin-checkout.c
+++ b/builtin-checkout.c

@@ -523,7 +523,10 @@ static void update_refs_for_switch(struct checkout_opts *opts,
 			   REF_NODEREF, DIE_ON_ERR);
 		if (!opts->quiet) {
 			if (old->path)
-				fprintf(stderr, "Note: moving to '%s' which isn't a local branch\nIf you want to create a new branch from this checkout, you may do so\n(now or later) by using -b with the checkout command again. Example:\n  git checkout -b <new_branch_name>\n", new->name);
+				fprintf(stderr, "Note: '%s' isn't a local branch head: creating a detached HEAD\n"
+						"If you want to create a new branch from this checkout, you may do so\n"
+						"(now or later) by using -b with the checkout command again. Example:\n"
+						"  git checkout -b <new_branch_name>\n", new->name);
 			describe_detached_head("HEAD is now at", new->commit);
 		}
 	}

(string split onto multiple lines for easier source reading)

I think this is important to 1) mention the notion of a branch _head_, 
and 2) mention "detached HEAD" explicitly for people to be directed to 
appropriate documentation.  So with this change you know exactly what 
happened and why.


Nicolas