Re: resolving a (possibly remote) branch HEAD to a hash

perryh@pluto.rain.com (Perry Hutchison) writes:

You are referring to this part of the documentation:

    If <branch> is not found but there does exist a tracking branch in
    exactly one remote (call it <remote>) with a matching name, treat as
    equivalent to

        $ git checkout -b <branch> --track <remote>/<branch>

A reader needs to read this part of the documentation a bit more carefully in order to notice that it never says it is equivalent to:

        $ git checkout -b <branch> -t <branch> ;# NOT CORRECT

This behaviour was brought in by somebody who thought that, in the context of "checkout" (and only in that context), it is clear that missing <branch> that can only mean the sole <remote>/<branch> and make that signal something more than what the user told "checkout" to do: "If you want to check out a <branch>, and it does not exist yet, you must wanted to create your own <branch> and start it at the same commit as somebody else has at the tip of his <branch>".

This "clever" dwim is very specific to the way you interact with "checkout" and generally does not apply when you want to run anything other than "checkout", e.g. "rev-parse" or "log".

But it is _so_ convenient a short-cut, that it lets new people form into an illusion that <branch> could be naming <remote>/<branch>. That is an incorrect perception.

The rationale behind "signal something more" above goes like this: if the user wanted to detach the head at the same commit as somebody else's <branch>, she would explicitly have written

	$ git checkout <remote>/<branch>

to do so. Because <remote>/<branch> is the shortest valid way to name that remote-tracking branch (i.e. exactly because <branch> is not a valid abbreviation for <remote>/<branch>), we can treat

	$ git checkout <branch>

when <branch> is not a local branch name specially.

It is sad and ironic that this checkout-specific DWIM works only because <branch> does not mean <remote>/<branch>, but presence of the DWIM gives a wrong illusion that it does X-<.