From: Matthias Lederhofer Date: Wed, 13 Jun 2007 05:41:36 GMT Subject: Re: [PATCH] make git barf when an alias changes environment variables Message-ID: <20070613054136.GA27476@moooo.ath.cx> In-Reply-To: <7vejkgh1jf.fsf@assigned-by-dhcp.pobox.com> Junio C Hamano 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.