Re: [PATCH] sha1_name: reorganize get_sha1_basic()

> Through the years the functionality to handle @{-N} and @{u} has moved
> around the code, and as a result, code that once made sense, doesn't any
> more.
>
> There is no need to call this function recursively with the branch of
> @{-N} substituted because dwim_{ref,log} already replaces it.
>
> However, there's one corner-case where @{-N} resolves to a detached
> HEAD, in which case we wouldn't get any ref back.
>
> So we parse the nth-prior manually, and deal with it depending on
> weather it's a SHA-1, or a ref.
>
> Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
> ---
>  sha1_name.c | 28 ++++++++++++++++------------
>  1 file changed, 16 insertions(+), 12 deletions(-)
>
> diff --git a/sha1_name.c b/sha1_name.c
> index 3820f28..110afbb 100644
> --- a/sha1_name.c
> +++ b/sha1_name.c
> @@ -431,6 +431,7 @@ static inline int upstream_mark(const char *string, int len)
>  }
>
>  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);
>
>  static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
>  {
> @@ -438,6 +439,7 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
>         char *real_ref = NULL;
>         int refs_found = 0;
>         int at, reflog_len;
> +       struct strbuf buf = STRBUF_INIT;
>
>         if (len == 40 && !get_sha1_hex(str, sha1))
>                 return 0;
> @@ -447,6 +449,9 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
>         if (len && str[len-1] == '}') {
>                 for (at = len-2; at >= 0; at--) {
>                         if (str[at] == '@' && str[at+1] == '{') {
> +                               if (at == 0 && str[2] == '-')
> +                                       /* @{-N} syntax */
> +                                       continue;
>                                 if (!upstream_mark(str + at, len - at)) {
>                                         reflog_len = (len-1) - (at+2);
>                                         len = at;
> @@ -460,20 +465,19 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
>         if (len && ambiguous_path(str, len))
>                 return -1;
>
> -       if (!len && reflog_len) {
> -               struct strbuf buf = STRBUF_INIT;
> -               int ret;
> -               /* try the @{-N} syntax for n-th checkout */
> -               ret = interpret_branch_name(str+at, &buf);
> -               if (ret > 0) {
> -                       /* substitute this branch name and restart */
> -                       return get_sha1_1(buf.buf, buf.len, sha1, 0);
> -               } else if (ret == 0) {
> -                       return -1;
> -               }
> +       if (interpret_nth_prior_checkout(str, &buf) > 0) {
> +               int detached;
> +
> +               detached = (buf.len == 40 && !get_sha1_hex(buf.buf, sha1));
> +               strbuf_release(&buf);
> +               if (detached)
> +                       return 0;
> +       }
> +
> +       if (!len && reflog_len)
>                 /* allow "@{...}" to mean the current branch reflog */
>                 refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
> -       } else if (reflog_len)
> +       else if (reflog_len)
>                 refs_found = dwim_log(str, len, sha1, &real_ref);
>         else
>                 refs_found = dwim_ref(str, len, sha1, &real_ref);
> --