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

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:

quoted

+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;
+}

...

quoted

+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).