Re: behaviour of git diff, GIT_DIR & checked out tree

On 9/24/07, Junio C Hamano [off-list ref] wrote:

It would be illustrative if David did the following.

        $ cd $HOME
        $ cp -a V W
        $ rm -fr W/.git
        $ cd W
        $ GIT_DIR=$HOME/V/.git git diff @{midnight}

Now we are in a random place outside of the work tree
(i.e. "W"), and we drive "git diff" with GIT_DIR specified,
telling it to pretend that we are at the top level of the work
tree.  So ~/W/frotz is compared with "frotz" at the top level of
the commit (which usually is compared with ~/V/frotz), etc.  But
the directory we happen to be in very much resembles the work
tree, so it would give identical results to

        $ cd $HOME/V
        $ git diff @{midnight}

To separate the two issues, I did all the commands to the diff
above and then removed one directory from the tree in W.

GIT_DIR=$HOME/V/.git git diff master~1
(which ought not need reflogs, right) and it gave a diff between
the contents of W and master~1. I also tried with commit
master@{midnight} and that also gave the difference between
W and the last commit yesterday. So Junio's explanation of what's going on
is right. I'm just asking if there's a way to say
"the `working dir' associated with this git dir" explicitly (in the same
way I can use `HEAD' to refer to the topmost commit on the
current branch) when you're not somewhere within the 'working dir'.
If there's not I can alias around it with
"cd $HOME/V && command && cd -". (As I say, for reasons unrelated
to git usage I don't actually "do work" within the tracked tree.)

Many thanks,

-- 
cheers, dave tweed__________________________
david.tweed@gmail.com
Rm 124, School of Systems Engineering, University of Reading.
"we had no idea that when we added templates we were adding a Turing-
complete compile-time language." -- C++ standardisation committee