Re: [WIP v1 2/4] mv: add check_dir_in_index() and solve general dir check issue

[Shaoxuan Yuan <shaoxuan.yuan02@gmail.com>]

On Fri, Apr 1, 2022 at 5:28 AM Victoria Dye <vdye@github.com> wrote:
>
> Shaoxuan Yuan wrote:
> > Originally, moving a <source> directory which is not on-disk due
> > to its existence outside of sparse-checkout cone, "giv mv" command
> > errors out with "bad source".
> >
> > Add a helper check_dir_in_index() function to see if a directory
> > name exists in the index. Also add a SPARSE_DIRECTORY bit to mark
> > such directories.
> >
>
> Hmm, I think this patch would fit better in your eventual "sparse index
> integration" series than this "prerequisite fixes to sparse-checkout"
> series. Sparse directories *only* appear when you're using a sparse index
> so, theoretically, this shouldn't ever come up (and thus isn't testable)
> until you're using a sparse index.

After reading your feedback, I realized that I totally misused
the phrase "sparse directory". Clearly, this patch series does not
deal with sparse-
index yet, as "sparse directory" is a cache entry that points to a
tree, if sparse-index
is enabled. Silly me ;)

What I was *actually* trying to say is: I want to change the checking
logic of moving
a "directory that exists outside of sparse-checkout cone", and I
apparently misused
"sparse directory" to reference such a thing.

> Since it's here, though, I'm happy to review what you have (even if you
> eventually move it to a later series)!

Thanks!

> > diff --git a/builtin/mv.c b/builtin/mv.c
> > index 32ad4d5682..9da9205e01 100644
> > --- a/builtin/mv.c
> > +++ b/builtin/mv.c
> > @@ -115,6 +115,25 @@ static int index_range_of_same_dir(const char *src, int length,
> >       return last - first;
> >  }
> >
> > +static int check_dir_in_index(const char *dir)
> > +{
>
> This function can be made a lot simpler - you can use `cache_name_pos()` to
> find the index entry - if it's found, the directory exists as a sparse
> directory. And, because 'add_slash()' enforces the trailing slash later on,
> you don't need to worry about adjusting the name before you look for the
> entry.

Yes, if I correctly used the phrase "sparse directory", but I did not...
I think I can use 'cache_name_pos()' to
check a directory *iff* it is a legit sparse directory when using sparse-index?

In my case, I just want to check a regular directory that is not in
the worktree,
since the cone pattern excludes it. And in a non-sparse index, cache
entry points only
to blobs, not trees, and that's the reason I wrote this weird function
to look into the
index. I understand that sounds not compatible with how git manages
index, but all
I want to know is "does this directory exist in the index?" (this
question is also quasi-correct).

I tried to find an existing API for this job, but I failed to find
any. Though I have a hunch
that there must be something to do it...

> > +     int ret = 0;
> > +     int length = sizeof(dir) + 1;
> > +     char *substr = malloc(length);
> > +
> > +     for (int i = 0; i < the_index.cache_nr; i++) {
> > +             memcpy(substr, the_index.cache[i]->name, length);
> > +             memset(substr + length - 1, 0, 1);
> > +
> > +             if (strcmp(dir, substr) == 0) {
> > +                     ret = 1;
> > +                     return ret;
> > +             }
> > +     }
> > +     free(substr);
> > +     return ret;
> > +}
> > +
> >  int cmd_mv(int argc, const char **argv, const char *prefix)
> >  {
> >       int i, flags, gitmodules_modified = 0;
> > @@ -129,7 +148,8 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
> >               OPT_END(),
> >       };
> >       const char **source, **destination, **dest_path, **submodule_gitfile;
> > -     enum update_mode { BOTH = 0, WORKING_DIRECTORY, INDEX, SPARSE } *modes;
> > +     enum update_mode { BOTH = 0, WORKING_DIRECTORY, INDEX, SPARSE,
> > +     SPARSE_DIRECTORY } *modes;
> >       struct stat st;
> >       struct string_list src_for_dst = STRING_LIST_INIT_NODUP;
> >       struct lock_file lock_file = LOCK_INIT;
> > @@ -197,6 +217,8 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
> >                        */
> >
> >                       int pos = cache_name_pos(src, length);
> > +                     const char *src_w_slash = add_slash(src);
> > +
> >                       if (pos >= 0) {
> >                               const struct cache_entry *ce = active_cache[pos];
> >
> > @@ -209,6 +231,11 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
> >                               else
> >                                       bad = _("bad source");
> >                       }
> > +                     else if (check_dir_in_index(src_w_slash) &&
> > +                     !path_in_sparse_checkout(src_w_slash, &the_index)) {
> > +                             modes[i] = SPARSE_DIRECTORY;
> > +                             goto dir_check;
> > +                     }
>
> In if-statements like this, you'll want to line up the statements in
> parentheses on subsequent lines, like:
>
>         else if (check_dir_in_index(src_w_slash) &&
>                  !path_in_sparse_checkout(src_w_slash, &the_index)) {
>
> ...where the second line is indented 1 (8-space-sized) tab + 1 space.
>
> In general, if you're trying to align code (in this repository), align first
> with as many tabs as possible, then the "remainder" with spaces. Note that
> this isn't 100% consistent throughout the repository - older lines might not
> have been aligned properly - but you should go for this styling on any new
> lines that you add.

Will do.

>
> >                       /* only error if existence is expected. */
> >                       else if (modes[i] != SPARSE)
> >                               bad = _("bad source");
> > @@ -219,7 +246,9 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
> >                               && lstat(dst, &st) == 0)
> >                       bad = _("cannot move directory over file");
> >               else if (src_is_dir) {
> > -                     int first = cache_name_pos(src, length), last;
> > +                     int first, last;
> > +dir_check:
> > +                     first = cache_name_pos(src, length);
> >
> >                       if (first >= 0)
> >                               prepare_move_submodule(src, first,
> > @@ -230,7 +259,8 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
> >                       else { /* last - first >= 1 */
> >                               int j, dst_len, n;
> >
> > -                             modes[i] = WORKING_DIRECTORY;
> > +                             if (!modes[i])
> > +                                     modes[i] = WORKING_DIRECTORY;
> >                               n = argc + last - first;
> >                               REALLOC_ARRAY(source, n);
> >                               REALLOC_ARRAY(destination, n);
> > @@ -332,7 +362,8 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
> >                       printf(_("Renaming %s to %s\n"), src, dst);
> >               if (show_only)
> >                       continue;
> > -             if (mode != INDEX && mode != SPARSE && rename(src, dst) < 0) {
> > +             if (mode != INDEX && mode != SPARSE && mode != SPARSE_DIRECTORY &&
> > +              rename(src, dst) < 0) {
> >                       if (ignore_errors)
> >                               continue;
> >                       die_errno(_("renaming '%s' failed"), src);
> > @@ -346,7 +377,7 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
> >                                                             1);
> >               }
> >
> > -             if (mode == WORKING_DIRECTORY)
> > +             if (mode == WORKING_DIRECTORY || mode == SPARSE_DIRECTORY)
>
> I'm a bit confused - doesn't this mean the sparse dir move will be skipped?
> In your commit description, you mention that this 'mv' succeeds with the
> '--sparse' option, but I don't see any place where the sparse directory
> would be moved.

Well, you know the drill, I did not use "sparse directory" correctly, let alone
'SPARSE_DIRECTORY' enum bit in this hunk. I think it makes some sense
if you apply my actual meaning of 'SPARSE_DIRECTORY' here (it should be
something like OUT_OF_CONE_WORKING_DIRECTORY)? Because such
directory is not on disk, it cannot be "rename()"d, and should also skip the
"rename_cache_entry_at()" function. If all the files under the directory are
moved/renamed, then (in my opinion) the directory is both moved to the
destination,
both in the worktree and in the index.

-- 
Thanks & Regards,
Shaoxuan