Re: [PATCH 3/8] merge-ort: record the reason that we want a rename for a directory

[Elijah Newren <newren@gmail.com>]

On Mon, Mar 15, 2021 at 7:31 AM Derrick Stolee <stolee@gmail.com> wrote:
>
> On 3/13/2021 5:22 PM, Elijah Newren via GitGitGadget wrote:
> > From: Elijah Newren <newren@gmail.com>
> >
> > When one side of history renames a directory, and the other side of
> > history added files to the old directory, directory rename detection is
> > used to warn about the location of the added files so the user can
> > move them to the old directory or keep them with the new one.
> >
> > This sets up three different types of directories:
> >   * directories that had new files added to them
> >   * directories underneath a directory that had new files added to them
> >   * directories where no new files were added to it or any leading path
> >
> > Save this information in dirs_removed; the next several commits will
> > make use of this information.
> ...
> > +/* dir_rename_relevance: the reason we want rename information for a dir */
> > +enum dir_rename_relevance {
> > +     NOT_RELEVANT = 0,
> > +     RELEVANT_FOR_ANCESTOR = 1,
> > +     RELEVANT_FOR_SELF = 2
> > +};
>
> Is this potentially a flag list? It's hard to tell because we don't
> have another item (3 or 4?).
>
> >               unsigned sides = (0x07 - dirmask)/2;
> > +             unsigned relevance = (renames->dir_rename_mask == 0x07) ?
> > +                                     RELEVANT_FOR_ANCESTOR : NOT_RELEVANT;
> > +             /*
> > +              * Record relevance of this directory.  However, note that
> > +              * when collect_merge_info_callback() recurses into this
> > +              * directory and calls collect_rename_info() on paths
> > +              * within that directory, if we find a path that was added
> > +              * to this directory on the other side of history, we will
> > +              * upgrade this value to RELEVANT_FOR_SELF; see below.
> > +              */
>
> This comment seems to imply that RELEVANT_FOR_SELF is "more important"
> than RELEVANT_FOR_ANCESTOR, so the value will just be changed (not a
> flag).

Yes.

> > +     /*
> > +      * Here's the block that potentially upgrades to RELEVANT_FOR_SELF.
> > +      * When we run across a file added to a directory.  In such a case,
> > +      * find the directory of the file and upgrade its relevance.
> > +      */
> > +     if (renames->dir_rename_mask == 0x07 &&
> > +         (filemask == 2 || filemask == 4)) {
> > +             /*
> > +              * Need directory rename for parent directory on other side
> > +              * of history from added file.  Thus
> > +              *    side = (~filemask & 0x06) >> 1
> > +              * or
> > +              *    side = 3 - (filemask/2).
> > +              */
> > +             unsigned side = 3 - (filemask >> 1);
> > +             strintmap_set(&renames->dirs_removed[side], dirname,
> > +                           RELEVANT_FOR_SELF);
>
> Yes, using "RELEVANT_FOR_SELF" here, not "relevance | RELEVANT_FOR_SELF".
> OK. This should make the later consumers simpler.

Yep, indeed.  Would it make it clearer earlier if I were to stop
assigning the explicit values in the enum?  Would adding a comment
when I introduce the enum be easier?  Or was it just "thinking out
loud"?