Re: [PATCH v4 20/21] refs: add LMDB refs storage backend

[David Turner <dturner@twopensource.com>]

On Sun, 2016-02-14 at 19:04 +0700, Duy Nguyen wrote:
> On Sat, Feb 6, 2016 at 2:44 AM, David Turner <
> dturner@twopensource.com> wrote:
> > +static char *get_refdb_path(const char *base)
> > +{
> > +       static struct strbuf path_buf = STRBUF_INIT;
> > +       strbuf_reset(&path_buf);
> > +       strbuf_addf(&path_buf, "%s/refdb", base);
> > +       return path_buf.buf;
> > +}
> ...
> > +static int lmdb_init_db(struct strbuf *err, int shared)
> > +{
> > +       /*
> > +        * To create a db, all we need to do is make a directory
> > for
> > +        * it to live in; lmdb will do the rest.
> > +        */
> > +
> > +       if (!db_path)
> > +               db_path =
> > xstrdup(real_path(get_refdb_path(get_git_common_dir())));
> 
> This works for multiple worktrees. But scripts may have harder time
> getting the path. The recommended way is "git rev-parse --git-path
> refdb" but because "refdb" is not registered in path.c:common_list[],
> that command becomes git_path("refdb") instead of
> get_refdb(get_git_... like here. And I will need to know that
> .git/refdb is _not_ per-worktree when I migrate/convert main worktree
> (it's very likely I have to go that route to solve .git/config issue
> in multi worktree).

I'll fix common_list.  

> The solution is register refdb to common_list[] and you can do
> git_path("refdb") here. But then what happens when another backend is
> added? Will the new backend use the same path "refdb", or say
> "refdb.sqlite"? If all backends share the name "refdb", why can't we
> just reuse "refs" instead because the default filesystem-based 
> backend is technically just another backend?

I'll change it to "refs.lmdb".

I don't want to use "refs" because it makes it hard for software to
distinguish the format (in some cases, like sqlite, it won't even be a
directory).