Re: user manual question

From: Daniel Barkalow <barkalow@iabervon.org>
Date: Dec 29, 2008, 19:30 UTC
Message-ID: <alpine.LNX.1.00.0812291358460.19665@iabervon.org>
In-Reply-To: <gjauel$94s$4@ger.gmane.org>

On Mon, 29 Dec 2008, Zorba wrote:

> so a detached HEAD is just a HEAD that is not sitting on a tip ?

If you used CVS (extensively) back in the day, a detached HEAD is like what you get if you do something like "cvs checkout -D yesterday" (CVS called it "sticky tags"); you have a working directory that contains some revision that isn't your latest revision. If you make changes, they can't go into the history in the normal fashion, but you can build the project and figure out how it worked back then.

With git, of course, you can do things you couldn't do from that state with CVS. Because git supports forking history, you can make commits and create a new branch to be on. Because git can handle having visibility into other people's branches, you can get a detached HEAD by checking out somebody else's branch (something like origin/next, for example).

The normal "attached HEAD" state is that there's some branch that you update when you make a commit; the "detached HEAD" state means that, when you make a commit, no branch is affected.

Show 5 quoted lines

> i.e. if I do $ git reset --hard HEAD^
> 
> ...pointing HEAD to the previous committ
> 
> this is a detached HEAD

Nope, it's "git checkout (something that isn't one of your branches)", just like CVS.

Git is like knitting. Commits are loops of yarn that hold other loops (their parents) in place; branches are knitting needles that keep new loops from falling out before other loops are holding them, and which hold different loops at different times as you work; HEAD is the tip of a needle that you use to make new loops. You usually use the tip of one of your regular needles to make new loops, and then the body of the needle holds the loop, but you could also use your fingers or something that will just make the loop temporarily; that's a detached HEAD, because it doesn't have the body of a needle behind it to hold loops when you use it for something else.

	-Daniel
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