Re: builtin command's prefix question

Junio C Hamano [off-list ref] writes:

 * I would say it is a misconfiguration if GIT_DIR is not set and
   GIT_WORK_TREE is, as the sole purpose of GIT_WORK_TREE is so that you
   can work from a subdirectory when you set GIT_DIR.  I may be missing
   an obvious use case that this is useful, but I do not think of any.
   Dscho may be able to correct me on this, as he fixed up the original
   work tree series that was even messier quite a bit during the last
   round.

I had a short discussion with Dscho on this.  One scenario that was
brought up was this.

You have a work tree of mixed contents that logically belong to
separate repository.  Think $HOME/.?*, and tracking .vimrc and
.pinerc as separate "projects".  You have $HOME/gits/vim.git and
$HOME/gits/pine.git bare-looking repositories.

The "kosher" way of doing this might be:

        $ cd $HOME
        $ GIT_WORK_TREE=$HOME; export GIT_WORK_TREE
        $ edit .vimrc
        $ GIT_DIR=gits/vim.git git commit .vimrc
        $ edit .pinerc
        $ GIT_DIR=gits/pine.git git commit .pinerc

However, if we define setup() to behave this way when GIT_DIR is not
defined and GIT_WORK_TREE is:

 (1) internally pretend as if GIT_DIR was specified to be the
     directory where the command was started from (iow, do getcwd()
     once upon startup);

 (2) chdir to GIT_WORK_TREE (which means "callers of setup() always
     run from the top of the work tree");

 (3) set prefix to NULL;

Then this workflow becomes possible:

	$ cd $HOME
        $ GIT_WORK_TREE=$HOME; export GIT_WORK_TREE
	$ edit .vimrc .pinerc
        $ cd $HOME/gits/vimrc.git && git commit .vimrc
        $ cd $HOME/gits/pinerc.git && git commit .pinerc

I am not convinced this is giving any natural user experience, nor an
alternative:

	$ cd $HOME
        $ GIT_WORK_TREE=$HOME; export GIT_WORK_TREE
        $ cd $HOME/gits/vimrc.git
	$ edit $HOME/.vimrc
        $ git commit .vimrc
        $ cd $HOME/gits/pinerc.git
	$ edit $HOME/.pinerc
        $ git commit .pinerc

While I still think the combination is simply crazy and does not make
any sense, if enough users on the list agrees that it makes sense, I
wouldn't mind setup() did (1) to (3) mentioned above.  The alternative
is simply to declare GIT_WORK_TREE without GIT_DIR is a nonsense and
either error error out or ignore GIT_WORK_TREE, which might be easier to
explain to people.

Opinions?