Re: [Outreachy][PATCH] abspath: reconcile `dir_exists()` and `is_directory()`

>
> On Thu, Oct 24, 2019 at 11:27:45AM +0200, Miriam Rubio wrote:
> > The dir_exists() function in builtin/clone.c is marked as static, so
> > nobody can use it outside builtin/clone.c.
> >
> > There is also is_directory() which obviously tries to do the very same, but it uses a name that few developers will think of when they see file_exists() and look for the equivalent function to see whether a given directory exists.
> >
> > Let's reconcile these functions by renaming is_directory() to dir_exists() and using it also in builtin/clone.c.
>
> Please wrap the proposed log message at about 70 characters width;
> that way it will look much better in 'git log' in a standard 80 char
> wide terminal.
>
> I think this is a cleanup worth doing, but...

>
> > diff --git a/abspath.c b/abspath.c
> > index 9857985329..13bd92eca5 100644
> > --- a/abspath.c
> > +++ b/abspath.c
> > @@ -5,7 +5,7 @@
> >   * symlink to a directory, we do not want to say it is a directory when
> >   * dealing with tracked content in the working tree.
> >   */
> > -int is_directory(const char *path)
> > +int dir_exists(const char *path)
> >  {
> >       struct stat st;
> >       return (!stat(path, &st) && S_ISDIR(st.st_mode));
>
> Note the '&& S_ISDIR(st.st_mode)', making sure that the given path is
> in fact a directory.  Good.
>
> > diff --git a/builtin/clone.c b/builtin/clone.c
> > index c46ee29f0a..f89938bf94 100644
> > --- a/builtin/clone.c
> > +++ b/builtin/clone.c
> > @@ -899,12 +899,6 @@ static void dissociate_from_references(void)
> >       free(alternates);
> >  }
> >
> > -static int dir_exists(const char *path)
> > -{
> > -     struct stat sb;
> > -     return !stat(path, &sb);
>
> But look at this, it only checks that the given path exists, but it
> could be a regular file or any other kind of path other than a
> directory as well!
>
> So this function clearly doesn't do what it's name suggests.  That's
> bad.
>
> Unfortunately, it gets worse: some of its callsites in
> 'builtin/clone.c' do expect it to check the existence of _any_ path,
> not just a directory.
>
> The first callsite is:
>
>     dest_exists = dir_exists(dir);
>     if (dest_exists && !is_empty_dir(dir))
>             die(_("destination path '%s' already exists and is not "
>                     "an empty directory."), dir);
>
> I think this actually means path_exists(): if a file, or any other
> kind of path with the given name were to exist, then we should die()
> showing this error message, but after changing dir_exists() to make
> sure that the path is indeed a directory we won't:
>
>   # create a 'git' _file_
>   $ >git
>   # current git master:
>   $ git clone https://github.com/git/git
>   fatal: destination path 'git' already exists and is not an empty directory.
>   # with this patch:
>   $ ~/src/git/git clone https://github.com/git/git
>   fatal: could not create work tree dir 'git': File exists
>
> So the command still fails, which is good, but with a different error
> message.  The test suite doesn't catch this, because the test case
> looking at this scenario ('clone to an existing path' in
> './t5601-clone.sh') only checks that 'git clone' fails, but it doesn't
> check whether it failed with the right error message.
>
> Now, that other error message comes after a failed mkdir() call later
> on which should have created the work tree.  So it begs the question
> what would happen when a file is in the way of a bare clone:
>
>   $ >git.git
>   $ git clone --bare https://github.com/git/git
>   fatal: destination path 'git.git' already exists and is not an empty directory.
>   $ ~/src/git/git clone --bare https://github.com/git/git
>   Cloning into bare repository 'git.git'...
>   fatal: invalid gitfile format: /home/szeder/src/git/tmp/git.git
>
> Then the next callsite looks like it meant path_exists() as well, but
> I didn't try to make it fail or show different behavior:
>
>     work_tree = getenv("GIT_WORK_TREE");
>     if (work_tree && dir_exists(work_tree))
>             die(_("working tree '%s' already exists."), work_tree);
>
> And there is a third callsite, but I'm not sure what it is about, and,
> consequently, what is really meant with dir_exists() here:
>
>     if (real_git_dir) {
>             if (dir_exists(real_git_dir))
>                     junk_git_dir_flags |= REMOVE_DIR_KEEP_TOPLEVEL;
>
>