Re: [PATCH 3/6] push: change `simple` to accommodate triangular workflows

> From: Ramkumar Ramachandra <artagnon@gmail.com>
>
> When remote.pushdefault or branch.<name>.pushremote is set (a triangular
> workflow feature), master@{u} != origin, and push.default is set to
> `upstream` or `simple`:
>
>   $ git push
>   fatal: You are pushing to remote 'origin', which is not the upstream of
>   your current branch 'master', without telling me what to push
>   to update which remote branch.
>
> The very name of "upstream" indicates that it is only suitable for
> use in central workflows; let us not even attempt to give it a new
> meaning in triangular workflows, and error out as usual.
>
> However, the `simple` does not have this problem: it is poised to be
> the default for Git 2.0, and we would definitely like it to do
> something sensible in triangular workflows.
>
> Redefine "simple" as "safer upstream" for centralized workflow as
> before, but work as "current" for triangular workflow.
>
> An earlier round of this change by mistake broke the safety for
> "simple" mode we have had since day 1 of that mode to make sure that
> the branch in the repository we update is set to be the one we fetch
> and integrate with, but it has been fixed.

> Reported-by: Leandro Lucarella <leandro.lucarella@sociomantic.com>
> Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---
>  Documentation/config.txt | 10 +++++++---
>  builtin/push.c           | 43 +++++++++++++++++++++++++++++++------------
>  2 files changed, 38 insertions(+), 15 deletions(-)
>
> diff --git a/Documentation/config.txt b/Documentation/config.txt
> index 5d8ff1a..cae6870 100644
> --- a/Documentation/config.txt
> +++ b/Documentation/config.txt
> @@ -1848,9 +1848,13 @@ push.default::
>    pushing to the same repository you would normally pull from
>    (i.e. central workflow).
>
> -* `simple` - like `upstream`, but refuses to push if the upstream
> -  branch's name is different from the local one. This is the safest
> -  option and is well-suited for beginners.
> +* `simple` - in centralized workflow, work like `upstream` with an
> +  added safety to refuse to push if the upstream branch's name is
> +  different from the local one.
> ++
> +When pushing to a remote that is different from the remote you normally
> +pull from, work as `current`.  This is the safest option and is suited
> +for beginners.
>  +
>  This mode will become the default in Git 2.0.
>
> diff --git a/builtin/push.c b/builtin/push.c
> index 2d84d10..f6c8047 100644
> --- a/builtin/push.c
> +++ b/builtin/push.c
> @@ -120,10 +120,11 @@ static const char message_detached_head_die[] =
>            "\n"
>            "    git push %s HEAD:<name-of-remote-branch>\n");
>
> -static void setup_push_upstream(struct remote *remote, int simple)
> +static void setup_push_upstream(struct remote *remote, struct branch *branch,
> +                               int triangular)
>  {
>         struct strbuf refspec = STRBUF_INIT;
> -       struct branch *branch = branch_get(NULL);
> +
>         if (!branch)
>                 die(_(message_detached_head_die), remote->name);
>         if (!branch->merge_nr || !branch->merge || !branch->remote_name)
> @@ -137,18 +138,29 @@ static void setup_push_upstream(struct remote *remote, int simple)
>         if (branch->merge_nr != 1)
>                 die(_("The current branch %s has multiple upstream branches, "
>                     "refusing to push."), branch->name);
> -       if (strcmp(branch->remote_name, remote->name))
> +       if (triangular)
>                 die(_("You are pushing to remote '%s', which is not the upstream of\n"
>                       "your current branch '%s', without telling me what to push\n"
>                       "to update which remote branch."),
>                     remote->name, branch->name);
> -       if (simple && strcmp(branch->refname, branch->merge[0]->src))
> -               die_push_simple(branch, remote);
> +
> +       if (push_default == PUSH_DEFAULT_SIMPLE) {
> +               /* Additional safety */
> +               if (strcmp(branch->refname, branch->merge[0]->src))
> +                       die_push_simple(branch, remote);
> +       }
>
>         strbuf_addf(&refspec, "%s:%s", branch->name, branch->merge[0]->src);
>         add_refspec(refspec.buf);
>  }
>
> +static void setup_push_current(struct remote *remote, struct branch *branch)
> +{
> +       if (!branch)
> +               die(_(message_detached_head_die), remote->name);
> +       add_refspec(branch->name);

> +}
> +
>  static char warn_unspecified_push_default_msg[] =
>  N_("push.default is unset; its implicit value is changing in\n"
>     "Git 2.0 from 'matching' to 'simple'. To squelch this message\n"
> @@ -173,9 +185,16 @@ static void warn_unspecified_push_default_configuration(void)
>         warning("%s\n", _(warn_unspecified_push_default_msg));
>  }
>
> +static int is_workflow_triagular(struct remote *remote)

> +}
> +
>  static void setup_default_push_refspecs(struct remote *remote)
>  {
> -       struct branch *branch;
> +       struct branch *branch = branch_get(NULL);
> +       int triangular = is_workflow_triagular(remote);
>
>         switch (push_default) {
>         default:
> @@ -188,18 +207,18 @@ static void setup_default_push_refspecs(struct remote *remote)
>                 break;
>
>         case PUSH_DEFAULT_SIMPLE:
> -               setup_push_upstream(remote, 1);
> +               if (triangular)
> +                       setup_push_current(remote, branch);
> +               else
> +                       setup_push_upstream(remote, branch, triangular);
>                 break;
>
>         case PUSH_DEFAULT_UPSTREAM:
> -               setup_push_upstream(remote, 0);
> +               setup_push_upstream(remote, branch, triangular);
>                 break;
>
>         case PUSH_DEFAULT_CURRENT:
> -               branch = branch_get(NULL);
> -               if (!branch)
> -                       die(_(message_detached_head_die), remote->name);
> -               add_refspec(branch->name);
> +               setup_push_current(remote, branch);
>                 break;
>
>         case PUSH_DEFAULT_NOTHING: