Subject: Re: Fetching tags overwrites existing tags

From: Junio C Hamano <[email-masked]>
Date: Fri, 27 Apr 2018 08:24:40 +0900

Junio C Hamano <[email-masked]> writes:

> Wink Saville <[email-masked]> writes:
>
>> I've tried to teach 'git remote add' the --prefix-tags option using the
>> technique Junio provided. At moment it is PR #486 on github [1]
>> and I'd love some comments on whether or not this the right direction
>> for fetching tags and putting them in the branches namespace.
>>
>> -- Wink
>>
>> [1] https://github.com/git/git/pull/486
>
> FWIW, here is how that pull/486/head looks like.
>
> -- >8 --
>
> From: Wink Saville <[email-masked]>
> Date: Thu, 26 Apr 2018 09:56:11 -0700
> Subject: [PATCH] Teach remote add the --prefix-tags option
>
> When --prefix-tags is passed to `git remote add` the tagopt is set to
> --prefix-tags and a second fetch line is added so tags are placed in
> the branches namespace.

When I hear "branches namespace", what comes to my mind is refs/heads/
or perhaps refs/remotes/*/.  "... are placed in a separate hierarchy
per remote" or something, perhaps?

>
> ...
> And the .git/config remote "gbenchmark" section looks like:
>   [remote "gbenchmark"]
>     url = [email-masked]:google/benchmark
>     fetch = +refs/heads/*:refs/remotes/gbenchmark/*
>     fetch = +refs/tags/*:refs/remote-tags/gbenchmark/*
>     tagopt = --prefix-tags
> ---

Missing sign-off ;-)

> +static void add_remote_tags(const char *key, const char *branchname,
> +		       const char *remotename, struct strbuf *tmp)
> +{
> +	strbuf_reset(tmp);
> +	strbuf_addch(tmp, '+');
> +	strbuf_addf(tmp, "refs/tags/%s:refs/remote-tags/%s/%s",
> +				branchname, remotename, branchname);

With "+refs/tags/%s:refs/remote-tags/%s/%s", combine addch/addf into
one, perhaps?

> +	git_config_set_multivar(key, tmp->buf, "^$", 0);
> +}

Calling the second parameter "branchname" makes little sense, I
would think.  Practically, you would call this at most once with its
second parameter set to '*', and even if the second parameter is not
a wildcard/asterisk, it would be a tagname.

>  static const char mirror_advice[] =
>  N_("--mirror is dangerous and deprecated; please\n"
>     "\t use --mirror=fetch or --mirror=push instead");
> @@ -161,6 +172,9 @@ static int add(int argc, const char **argv)
>  		OPT_SET_INT(0, "tags", &fetch_tags,
>  			    N_("import all tags and associated objects when fetching"),
>  			    TAGS_SET),
> +		OPT_SET_INT(0, "prefix-tags", &fetch_tags,
> +			    N_("import all tags and associated objects when fetching and prefix with <name>"),
> +          TAGS_SET_PREFIX),

Funny indent.  Use monospaced font in your editor, set tab width to
8 and align, imitating how the above OPT_SET_INT() item does for
TAGS_SET.

> @@ -215,10 +229,35 @@ static int add(int argc, const char **argv)
>  	}
>  
>  	if (fetch_tags != TAGS_DEFAULT) {
> +		if (fetch_tags == TAGS_SET_PREFIX) {
> +			strbuf_reset(&buf);
> +			strbuf_addf(&buf, "remote.%s.fetch", name);
> +			if (track.nr == 0)
> +				string_list_append(&track, "*");
> +			for (i = 0; i < track.nr; i++) {
> +				add_remote_tags(buf.buf, track.items[i].string,
> +						name, &buf2);
> +			}

The "track" thing is made incompatible with anything but mirror in
early part of this function (outside the precontext).  I highly
suspect that --prefix-tags does *not* make sense when mirroring.

Hence (1) we should detect and error out when --prefix-tags is used
with mirror fetch near where we do the same for track used without
mirror fetch already, (2) detect and error out when --prefix-tags is
used with track, and (3) add "+refs/tags/*:refs/remote-tags/$name/*"
just once without paying attention to track here.  We may not even
want add_remote_tags() helper function if we go that route.

> +		}
> +
>  		strbuf_reset(&buf);
>  		strbuf_addf(&buf, "remote.%s.tagopt", name);
> -		git_config_set(buf.buf,
> -			       fetch_tags == TAGS_SET ? "--tags" : "--no-tags");
> +		char* config_val = NULL;

decl-after-statement.  Also "char *var", not "char* var".

> +		switch (fetch_tags) {
> +		case TAGS_UNSET:
> +			config_val = "--no-tags";
> +			break;
> +		case TAGS_SET:
> +			config_val = "--tags";
> +			break;
> +		case TAGS_SET_PREFIX:
> +			config_val = "--prefix-tags";
> +			break;
> +		default:
> +			die(_("Unexpected TAGS enum %d"), fetch_tags);
> +			break;
> +		}
> +		git_config_set(buf.buf, config_val);
>  	}
>  
>  	if (fetch && fetch_remote(name))
> diff --git a/remote.c b/remote.c
> index 91eb010ca9..f383ce3cdf 100644
> --- a/remote.c
> +++ b/remote.c
> @@ -447,6 +447,8 @@ static int handle_config(const char *key, const char *value, void *cb)
>  			remote->fetch_tags = -1;
>  		else if (!strcmp(value, "--tags"))
>  			remote->fetch_tags = 2;
> +		else if (!strcmp(value, "--prefix-tags"))
> +			remote->fetch_tags = -1; // A fetch for refs/tags is present so tags are retrieved

We are old fashioned and do not use // comments, but more
importantly it is not clear what this comment is trying to
say, at least to me.

>  	} else if (!strcmp(subkey, "proxy")) {
>  		return git_config_string((const char **)&remote->http_proxy,
>  					 key, value);