Re: [RFC PATCH] fast-export, fast-import: Let tags specify an internal name

[Luke Shumaker <lukeshu@lukeshu.com>]

On Wed, 21 Apr 2021 02:03:57 -0600,
Ævar Arnfjörð Bjarmason wrote:
> On Tue, Apr 20 2021, Luke Shumaker wrote:
> 
> > -static void handle_tag(const char *name, struct tag *tag)
> > +static void handle_tag(const char *refname, struct tag *tag)
> >  {
> >  	unsigned long size;
> >  	enum object_type type;
> >  	char *buf;
> > -	const char *tagger, *tagger_end, *message;
> > +	const char *refbasename;
> > +	const char *tagname, *tagname_end, *tagger, *tagger_end, *message;
> 
> Let's put the new "*tagname, *tagname_end" on its own line, the current
> convention is to not conflate unrelated variable declarations on the
> same line (as e.g. the existing "message" and "tagger" does.

Ack.

> >  	size_t message_size = 0;
> >  	struct object *tagged;
> >  	int tagged_mark;
> > @@ -800,6 +801,11 @@ static void handle_tag(const char *name, struct tag *tag)
> >  		message += 2;
> >  		message_size = strlen(message);
> >  	}
> > +	tagname = memmem(buf, message ? message - buf : size, "\ntag ", 5);
> > +	if (!tagname)
> > +		die("malformed tag %s", oid_to_hex(&tag->object.oid));
> > +	tagname += 5;
> > +	tagname_end = strchrnul(tagname, '\n');
> 
> So it's no longer possible to export a reporitory with a missing "tag"
> entry in a tag? Maybe OK, but we have an escape hatch for it with fsck,
> we don't need one here?
> 
> In any case a test for it would be good to have.

I hadn't realized that it was possible for a tag object to be missing
the "tag" entry, I will fix that.

I don't think it's worth adding an option to fast-import to make it
possible to create such an object, but fast-export should be able to
handle it (and emit it in the stream such that fast-import would
create it with the "tag" entry").

Yes, the whole patch needs tests.

> > @@ -884,14 +890,19 @@ static void handle_tag(const char *name, struct tag *tag)
> >  
> >  	if (tagged->type == OBJ_TAG) {
> >  		printf("reset %s\nfrom %s\n\n",
> > -		       name, oid_to_hex(&null_oid));
> > +		       refname, oid_to_hex(&null_oid));
> >  	}
> > -	skip_prefix(name, "refs/tags/", &name);
> > -	printf("tag %s\n", name);
> > +	refbasename = refname;
> > +	skip_prefix(refbasename, "refs/tags/", &refbasename);
> > +	printf("tag %s\n", refbasename);
> >  	if (mark_tags) {
> >  		mark_next_object(&tag->object);
> >  		printf("mark :%"PRIu32"\n", last_idnum);
> >  	}
> > +	if ((size_t)(tagname_end - tagname) != strlen(refbasename) ||
> 
> Would be more readable IMO to have a temporary variable for that
> "tagname_end - tagname", then just cast that and use it here.
> 
> > +	    strncmp(tagname, refbasename, (size_t)(tagname_end - tagname)))
> 
> and here.

Ack.

> > @@ -2803,6 +2803,13 @@ static void parse_new_tag(const char *arg)
> >  	read_next_command();
> >  	parse_mark();
> >  
> > +	/* name ... */
> > +	if (skip_prefix(command_buf.buf, "name ", &v)) {
> > +		name = strdupa(v);
> > +		read_next_command();
> > +	} else
> > +		name = NULL;
> > +
> 
> Skip this whole (stylistically incorrect, should have {}) and just
> initialize it to NULL when you declare the variable?

In my defense, the guideline has always been to match the local style,
and in fast-import.c this is done without {} 8 times and with {} 3
times :)

-- 
Happy hacking,
~ Luke Shumaker