Re: [PATCH 5/5] implement @{publish} shorthand

> In a triangular workflow, you may have a distinct
> @{upstream} that you pull changes from, but publish by
> default (if you typed "git push") to a different remote (or
> a different branch on the remote). It may sometimes be
> useful to be able to quickly refer to that publishing point
> (e.g., to see which changes you have that have not yet been
> published).
>
> This patch introduces the <branch>@{publish} shorthand (or
> "@{pu}" to be even shorter). It refers to the tracking

> branch of the remote branch to which you would push if you
> were to push the named branch. That's a mouthful to explain,
> so here's an example:
>
>   $ git checkout -b foo origin/master
>   $ git config remote.pushdefault github
>   $ git push
>
> Signed-off-by: Jeff King <peff@peff.net>
> ---
> The implementation feels weird, like the "where do we push to" code
> should be factored out from somewhere else. I think what we're doing
> here is not _wrong_, but I don't like repeating what "git push" is doing
> elsewhere. And I just punt on "simple" as a result. :)
>
>  sha1_name.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 75 insertions(+), 1 deletion(-)
>
> diff --git a/sha1_name.c b/sha1_name.c
> index 50df5d4..59ffa93 100644
> --- a/sha1_name.c
> +++ b/sha1_name.c
> @@ -435,6 +435,12 @@ static inline int upstream_mark(const char *string, int len)
>  	return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
>  }
>  
> +static inline int publish_mark(const char *string, int len)
> +{
> +	const char *suffix[] = { "@{publish}" };
> +	return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
> +}
> +
>  static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned lookup_flags);
>  static int interpret_nth_prior_checkout(const char *name, struct strbuf *buf);
>  
> @@ -481,7 +487,8 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
>  					nth_prior = 1;
>  					continue;
>  				}
> -				if (!upstream_mark(str + at, len - at)) {
> +				if (!upstream_mark(str + at, len - at) &&
> +				    !publish_mark(str + at, len - at)) {
>  					reflog_len = (len-1) - (at+2);
>  					len = at;
>  				}
> @@ -1100,6 +1107,69 @@ static int interpret_upstream_mark(const char *name, int namelen,
>  	return len + at;
>  }
>  
> +static const char *get_publish_branch(const char *name_buf, int len)
> +{
> +	char *name = xstrndup(name_buf, len);
> +	struct branch *b = branch_get(*name ? name : NULL);
> +	struct remote *remote = b->pushremote;
> +	const char *dst;
> +	const char *track;
> +
> +	free(name);
> +
> +	if (!remote)
> +		die(_("branch '%s' has no remote for pushing"), b->name);
> +
> +	/* Figure out what we would call it on the remote side... */
> +	if (remote->push_refspec_nr)
> +		dst = apply_refspecs(remote->push, remote->push_refspec_nr,
> +				     b->refname);
> +	else
> +		dst = b->refname;
> +	if (!dst)
> +		die(_("unable to figure out how '%s' would be pushed"),
> +		    b->name);
> +
> +	/* ...and then figure out what we would call that remote here */
> +	track = apply_refspecs(remote->fetch, remote->fetch_refspec_nr, dst);
> +	if (!track)
> +		die(_("%s@{publish} has no tracking branch for '%s'"),
> +		    b->name, dst);
> +
> +	return track;
> +}
> +
> +static int interpret_publish_mark(const char *name, int namelen,
> +				  int at, struct strbuf *buf)
> +{
> +	int len;
> +
> +	len = publish_mark(name + at, namelen - at);
> +	if (!len)
> +		return -1;
> +
> +	switch (push_default) {
> +	case PUSH_DEFAULT_NOTHING:
> +		die(_("cannot use @{publish} with push.default of 'nothing'"));
> +
> +	case PUSH_DEFAULT_UNSPECIFIED:
> +	case PUSH_DEFAULT_MATCHING:
> +	case PUSH_DEFAULT_CURRENT:
> +		set_shortened_ref(buf, get_publish_branch(name, at));
> +		break;
> +
> +	case PUSH_DEFAULT_UPSTREAM:
> +		set_shortened_ref(buf, get_upstream_branch(name, at));
> +		break;
> +
> +	case PUSH_DEFAULT_SIMPLE:
> +		/* ??? */
> +		die("@{publish} with simple unimplemented");
> +	}
> +
> +	return at + len;
> +}
> +
>  /*
>   * This reads short-hand syntax that not only evaluates to a commit
>   * object name, but also can act as if the end user spelled the name
> @@ -1150,6 +1220,10 @@ int interpret_branch_name(const char *name, int namelen, struct strbuf *buf)
>  	if (len > 0)
>  		return len;
>  
> +	len = interpret_publish_mark(name, namelen, cp - name, buf);
> +	if (len > 0)
> +		return len;
> +
>  	return -1;
>  }