Re: [PATCHv5 7/8] clone: implement optional references

> Signed-off-by: Stefan Beller <sbeller@google.com>
> ---
>  Documentation/git-clone.txt |  5 ++++-
>  builtin/clone.c             | 35 +++++++++++++++++++++++++----------
>  2 files changed, 29 insertions(+), 11 deletions(-)
>
> diff --git a/Documentation/git-clone.txt b/Documentation/git-clone.txt
> index ec41d3d..e316c4b 100644
> --- a/Documentation/git-clone.txt
> +++ b/Documentation/git-clone.txt
> @@ -90,13 +90,16 @@ If you want to break the dependency of a repository cloned with `-s` on
>  its source repository, you can simply run `git repack -a` to copy all
>  objects from the source repository into a pack in the cloned repository.
>
> ---reference <repository>::
> +--reference[-if-able] <repository>::
>         If the reference repository is on the local machine,
>         automatically setup `.git/objects/info/alternates` to
>         obtain objects from the reference repository.  Using
>         an already existing repository as an alternate will
>         require fewer objects to be copied from the repository
>         being cloned, reducing network and local storage costs.
> +       When using the `--reference-if-able`, a non existing
> +       directory is skipped with a warning instead of aborting
> +       the clone.
>  +
>  *NOTE*: see the NOTE for the `--shared` option, and also the
>  `--dissociate` option.
> diff --git a/builtin/clone.c b/builtin/clone.c
> index ef5db7c..0182665 100644
> --- a/builtin/clone.c
> +++ b/builtin/clone.c
> @@ -51,6 +51,7 @@ static int option_progress = -1;
>  static enum transport_family family;
>  static struct string_list option_config = STRING_LIST_INIT_NODUP;
>  static struct string_list option_required_reference = STRING_LIST_INIT_NODUP;
> +static struct string_list option_optional_reference = STRING_LIST_INIT_NODUP;
>  static int option_dissociate;
>  static int max_jobs = -1;
>
> @@ -81,6 +82,8 @@ static struct option builtin_clone_options[] = {
>                    N_("directory from which templates will be used")),
>         OPT_STRING_LIST(0, "reference", &option_required_reference, N_("repo"),
>                         N_("reference repository")),
> +       OPT_STRING_LIST(0, "reference-if-able", &option_optional_reference,
> +                       N_("repo"), N_("reference repository")),
>         OPT_BOOL(0, "dissociate", &option_dissociate,
>                  N_("use --reference only while cloning")),
>         OPT_STRING('o', "origin", &option_origin, N_("name"),
> @@ -283,24 +286,36 @@ static void strip_trailing_slashes(char *dir)
>  static int add_one_reference(struct string_list_item *item, void *cb_data)
>  {
>         struct strbuf err = STRBUF_INIT;
> -       struct strbuf sb = STRBUF_INIT;
> +       int *required = cb_data;
>         char *ref_git = compute_alternate_path(item->string, &err);
>
> -       if (!ref_git)
> -               die("%s", err.buf);
> -
> -       strbuf_addf(&sb, "%s/objects", ref_git);
> -       add_to_alternates_file(sb.buf);
> +       if (!ref_git) {
> +               if (*required)
> +                       die("%s", err.buf);
> +               else
> +                       fprintf(stderr,
> +                               _("info: Could not add alternate for '%s': %s\n"),
> +                               item->string, err.buf);
> +       } else {
> +               struct strbuf sb = STRBUF_INIT;
> +               strbuf_addf(&sb, "%s/objects", ref_git);
> +               add_to_alternates_file(sb.buf);
> +               strbuf_release(&sb);
> +       }