Junio C Hamano <gitster@xxxxxxxxx> wrote:
> What does this patch do when you do this?
>
> : Because I usually work with this repository...
> $ GIT_DIR=$some_repository
> $ export GIT_DIR
>
> : Then much later, I happen to visit another repository
> : to take a peek...
> $ cd $somewhere_else
> $ git --git-dir .git some-command
>
This one has no alias involved as far as I see, so there is no change.
The patch makes git barf when an alias changes the environment (i.e.
an alias uses --git-dir/--work-tree/--bare). When git has read the
configuration file to find out about aliases setup_git_env has been
called and a pointer returned by getenv("GIT_DIR") is already stored
in a static pointer. If the environment variable is changed
afterwards git might or might not use the new value depending on the
implementation.
That is what my example shows: FreeBSD libc reuses the old memory
location if the new value of an environment variable fits in the old
place. Because setup_git_env uses xstrdup on the object dir and some
other directories the old value is used for those but the new one is
used for git_dir (which is just a pointer returned by getenv). This
way HEAD is read from the new repository but objects are searched in
the old repository.
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