Re: [PATCH] refs.c: interpret @ as HEAD

[Duy Nguyen <pclouds@gmail.com>]

On Tue, Apr 30, 2013 at 03:01:22PM +0200, Thomas Rast wrote:
> > This patch has the exact same effect as:
> >
> >     $ git symbolic-ref @ HEAD
> 
> But then why don't you just 'git symbolic-ref H HEAD' for a sort of
> "local alias"?

For me, it's because I don't want to do that on every repo. One day if
I change my mind and make P the new alias, i'll need to update every
repo again.

> 
> What annoys me more is that there's no way to say
> 
>   git symbolic-ref U @{u}
> 
> so that I can avoid that -- it's really clumsy to type on a Swiss German
> keyboard.  We'd need some sort of ref-alias feature for that to work.

It's not hard to do. The below patch makes "." equivalent to HEAD and
".U" -> "@{u}". Refs are not supposed to have '.' at the beginning, so
it's easy to figure somebody is using alias from what they send
you. Supporting refalias.* config should be easy.

-- 8< --
diff --git a/sha1_name.c b/sha1_name.c
index 3820f28..7842147 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -1239,6 +1239,27 @@ static char *resolve_relative_path(const char *rel)
 			   rel);
 }
 
+static int get_sha1_with_alias(const char *name, int namelen,
+			       unsigned char *sha1, int flags)
+{
+	int ret;
+	struct strbuf sb = STRBUF_INIT;
+	int alias_len = strcspn(name, "@^~:");
+	if (alias_len > namelen)
+		alias_len = namelen;
+
+	if (alias_len == 0)	/* '.' is equal to HEAD */
+		strbuf_addstr(&sb, "HEAD");
+	else if (alias_len == 1 && !strncmp(name, "U", 1))
+		strbuf_addstr(&sb, "@{u}");
+	else
+		return error("unknown alias %.*s", alias_len, name);
+	strbuf_addstr(&sb, name + alias_len);
+	ret = get_sha1_1(sb.buf, sb.len, sha1, flags);
+	strbuf_release(&sb);
+	return ret;
+}
+
 static int get_sha1_with_context_1(const char *name,
 				   unsigned flags,
 				   const char *prefix,
@@ -1252,6 +1273,8 @@ static int get_sha1_with_context_1(const char *name,
 
 	memset(oc, 0, sizeof(*oc));
 	oc->mode = S_IFINVALID;
+	if (name[0] == '.')
+		return get_sha1_with_alias(name + 1, namelen - 1, sha1, flags);
 	ret = get_sha1_1(name, namelen, sha1, flags);
 	if (!ret)
 		return ret;
-- 8< --