patchsha1_name.c: add an option to abort on ambiguous refs

> Hi Duy,
>
> On Wed, 23 Mar 2016, Nguyễn Thái Ngọc Duy wrote:
>
>> There are cases when a warning on ambiguous refs may go unnoticed
>> (e.g. git-log filling up the whole screen). There are also cases when
>> people want to catch ambiguity early (e.g. it happens deep in some
>> script). In either case, aborting the program would accomplish it.
>
> Whenever I see a die() in code outside of builtin/*.c, I cringe. I do that
> because it was *exactly* something like that that caused a serious
> regression in the builtin am so that we had to resort back to spawning
> separate processes *just so* that we could catch error conditions and
> run certain code in that case.
>
> Maybe there would be a way to do what you want to do that does not fly in
> the face of libification?

> There are cases when a warning on ambiguous refs may go unnoticed
> (e.g. git-log filling up the whole screen). There are also cases when
> people want to catch ambiguity early (e.g. it happens deep in some
> script). In either case, aborting the program would accomplish it.
>
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
>  Documentation/config.txt |  3 ++-
>  config.c                 |  5 ++++-
>  sha1_name.c              | 10 ++++++++--
>  3 files changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/config.txt b/Documentation/config.txt
> index 2cd6bdd..4172f59 100644
> --- a/Documentation/config.txt
> +++ b/Documentation/config.txt
> @@ -522,7 +522,8 @@ core.sharedRepository::
>
>  core.warnAmbiguousRefs::
>         If true, Git will warn you if the ref name you passed it is ambiguous
> -       and might match multiple refs in the repository. True by default.
> +       and might match multiple refs in the repository. If set to "fatal",
> +       the program will abort on ambiguous refs. True by default.
>
>  core.compression::
>         An integer -1..9, indicating a default compression level.
> diff --git a/config.c b/config.c
> index 9ba40bc..79f1ea5 100644
> --- a/config.c
> +++ b/config.c
> @@ -738,7 +738,10 @@ static int git_default_core_config(const char *var, const char *value)
>         }
>
>         if (!strcmp(var, "core.warnambiguousrefs")) {
> -               warn_ambiguous_refs = git_config_bool(var, value);
> +               if (!strcasecmp(value, "fatal"))
> +                       warn_ambiguous_refs = 2;
> +               else
> +                       warn_ambiguous_refs = git_config_bool(var, value);
>                 return 0;
>         }
>
> diff --git a/sha1_name.c b/sha1_name.c
> index 3acf221..a0f0ab9 100644
> --- a/sha1_name.c
> +++ b/sha1_name.c
> @@ -480,6 +480,8 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1,
>                                 warning(warn_msg, len, str);
>                                 if (advice_object_name_warning)
>                                         fprintf(stderr, "%s\n", _(object_name_msg));
> +                               if (warn_ambiguous_refs > 1)
> +                                       die(_("cannot continue with ambiguous refs"));
>                         }
>                         free(real_ref);
>                 }
> @@ -537,8 +539,12 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1,
>
>         if (warn_ambiguous_refs && !(flags & GET_SHA1_QUIETLY) &&
>             (refs_found > 1 ||
> -            !get_short_sha1(str, len, tmp_sha1, GET_SHA1_QUIETLY)))
> -               warning(warn_msg, len, str);
> +            !get_short_sha1(str, len, tmp_sha1, GET_SHA1_QUIETLY))) {
> +               if (warn_ambiguous_refs > 1)
> +                       die(warn_msg, len, str);
> +               else
> +                       warning(warn_msg, len, str);
> +       }
>
>         if (reflog_len) {
>                 int nth, i;
> --
> 2.8.0.rc0.210.gd302cd2
>