Johannes Schindelin schrieb:
> Hi,
>
> On Wed, 6 Feb 2008, Johannes Sixt wrote:
>
>> Jeff King schrieb:
>>> In setup_git_directory_gently, we have a special rule that says "if
>>> GIT_DIR is set but GIT_WORK_TREE is not, then use the current working
>>> directory as the work tree." This is the intended behavior for the
>>> user perspective.
>>>
>>> However, setup_git_directory_gently sets GIT_DIR itself, meaning that
>>> further setups (either because we are executing a command via alias,
>>> or in a subprocess) will see the non-existent GIT_WORK_TREE and assume
>>> we fall into the "current working directory is the working tree"
>>> codepath.
>>>
>>> Instead, we now use a special value of GIT_WORK_TREE to indicate that
>>> we have already checked for a worktree and that there isn't one,
>>> setting it when we set GIT_DIR and checking for it in the special case
>>> path.
>>>
>>> The special value is a blank GIT_WORK_TREE; it could be any value, but
>>> this should not conflict with any user values (and as a bonus, you can
>>> now tell git "I don't have a work tree" with "GIT_WORK_TREE= git",
>>> though I suspect the use case for that is limited).
>> Hrm. Unfortunately, on Windows there is no such thing as an empty
>> environment string. setenv(x, "") *removes* the environment variable.
>
> That might be a shortcoming of our implementation of setenv():
No, it is not. It's Windows's putenv(), and it's even documented.
> -- snip --
> cd /git
>
> cat > a1.c << EOF
> #include <stdio.h>
> #include "compat/setenv.c"
> #include "compat/unsetenv.c"
>
> static void p()
> {
> const char *abc = getenv("ABC");
> printf("env ABC: %s\n", abc ? abc : "(null)");
> }
>
> int main()
> {
> p();
> gitsetenv("ABC", "Hello", 1);
> p();
> gitsetenv("ABC", "", 1);
> p();
> gitunsetenv("ABC");
> p();
> return 0;
> }
> EOF
>
> gcc -DNO_MMAP=1 -I. -Icompat -o a1.exe a1.c
>
> ABC="" ./a1.exe
> -- snap --
>
> This will show
>
> env ABC:
> env ABC: Hello
> env ABC: (null)
> env ABC: (null)
>
> So it seems that environment variables _can_ be empty. Just our
> relatively stupid implementation of setenv() does not do it.
>
> Maybe something like compat/unsetenv.c is needed in setenv(), too.
This only shows that, yes, variables _can_ be empty - if the setenv/putenv
implementation is "sane", like MSYS/bash's.
That said, we probably should modify environ directly in gitsetenv().
-- Hannes
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