Re: [PATCH 4/4] submodule: port submodule subcommand 'summary' from shell to C

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Shourya,

On Thu, 16 Jul 2020, Shourya Shukla wrote:

> BTW in your review of my patch,
> https://lore.kernel.org/git/nycvar.QRO.7.76.6.2007031712160.50@tvgsbejvaqbjf.bet/
> you said this:
> --------------->8--------------
> > +			 */
> > +			struct child_process cp_rev_parse = CHILD_PROCESS_INIT;
> > +			struct strbuf sb_rev_parse = STRBUF_INIT;
> > +
> > +			cp_rev_parse.git_cmd = 1;
> > +			cp_rev_parse.no_stderr = 1;
> > +			cp_rev_parse.dir = p->sm_path;
> > +			prepare_submodule_repo_env(&cp_rev_parse.env_array);
> > +
> > +			argv_array_pushl(&cp_rev_parse.args, "rev-parse",
> > +					 "HEAD", NULL);
> > +			if (!capture_command(&cp_rev_parse, &sb_rev_parse, 0)) {
> > +				strbuf_strip_suffix(&sb_rev_parse, "\n");
> > +				get_oid_hex(sb_rev_parse.buf, &p->oid_dst);
> > +			}
> > +			strbuf_release(&sb_rev_parse);
> > +		} else if (S_ISLNK(p->mod_dst) || S_ISREG(p->mod_dst)) {
> > +			struct child_process cp_hash_object = CHILD_PROCESS_INIT;
> > +			struct strbuf sb_hash_object = STRBUF_INIT;
> > +
> > +			cp_hash_object.git_cmd = 1;
> > +			argv_array_pushl(&cp_hash_object.args, "hash-object",
> > +					 p->sm_path, NULL);
> > +			if (!capture_command(&cp_hash_object,
> > +					     &sb_hash_object, 0)) {
> > +				strbuf_strip_suffix(&sb_hash_object, "\n");
> > +				get_oid_hex(sb_hash_object.buf, &p->oid_dst);
> > +			}
> > +			strbuf_release(&sb_hash_object);
>
> It would probably be shorter, less error-prone, and quicker to use
> `index_fd()` directly.
> --------------->8--------------
>
> What exactly did you mean here and where should the index_fd() be used?

Well, `index_fd()` is the function that `git hash-object` uses to
calculate the hash of a given file (in this case, specified via the path
`p->sm_path`).

You could open an fd to that file directly, use `index_fd()` to calculate
the hash, and thereby avoid spawning another (totally unnecessary)
process.

Ciao,
Dscho