Re: [PATCH v2 10/14] pull: add proper error with --ff-only

[Elijah Newren <newren@gmail.com>]

On Thu, Dec 3, 2020 at 10:16 PM Felipe Contreras
<felipe.contreras@gmail.com> wrote:
>
> The current error is not user-friendly:
>
>   fatal: not possible to fast-forward, aborting.
>
> We want something that actually explains what is going on:
>
>   The pull was not fast-forward, please either merge or rebase.
>   If unsure, run "git pull --merge".

Sorry to be a broken record, but I don't like the suggestion in the
second sentence.  I've said it enough times that I'll quit harping on
each instance.

> The user can get rid of the warning by doing either --merge or
> --rebase.
>
> Except: doing "git pull --merge" is not actually enough; we would return
> to the previous behavior: "fatal: not possible to fast-forward, aborting."

Do you mean that the changes in this patch aren't enough and that
future patches will address this shortcoming?  Or do you mean that
prior to this patch such a bug existed?  Or something else?

>
> Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
> ---
>  builtin/pull.c  | 34 ++++++++++++++++-----------
>  t/t5520-pull.sh | 62 +++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 82 insertions(+), 14 deletions(-)
>
> diff --git a/builtin/pull.c b/builtin/pull.c
> index 6ea95c9fc9..f54ff36b57 100644
> --- a/builtin/pull.c
> +++ b/builtin/pull.c
> @@ -1015,20 +1015,26 @@ int cmd_pull(int argc, const char **argv, const char *prefix)
>
>         can_ff = get_can_ff(&orig_head, &merge_heads.oid[0]);
>
> -       if (default_mode && !can_ff && opt_verbosity >= 0 && !opt_ff) {
> -               advise(_("Pulling without specifying how to reconcile divergent branches is\n"
> -                       "discouraged; you need to specify if you want a merge, or a rebase.\n"
> -                       "You can squelch this message by running one of the following commands:\n"
> -                       "\n"
> -                       "  git config pull.rebase false  # merge (the default strategy)\n"
> -                       "  git config pull.rebase true   # rebase\n"
> -                       "  git config pull.ff only       # fast-forward only\n"
> -                       "\n"
> -                       "You can replace \"git config\" with \"git config --global\" to set a default\n"
> -                       "preference for all repositories.\n"
> -                       "If unsure, run \"git pull --merge\".\n"
> -                       "Read \"git pull --help\" for more information."
> -                       ));
> +       if (!can_ff && default_mode) {
> +               if (opt_ff && !strcmp(opt_ff, "--ff-only")) {
> +                       die(_("The pull was not fast-forward, please either merge or rebase.\n"
> +                               "If unsure, run \"git pull --merge\"."));

This is a much better message for when the user requests --ff-only.

> +               }
> +               if (opt_verbosity >= 0 && !opt_ff) {
> +                       advise(_("Pulling without specifying how to reconcile divergent branches is\n"
> +                               "discouraged; you need to specify if you want a merge, or a rebase.\n"
> +                               "You can squelch this message by running one of the following commands:\n"
> +                               "\n"
> +                               "  git config pull.rebase false  # merge (the default strategy)\n"
> +                               "  git config pull.rebase true   # rebase\n"
> +                               "  git config pull.ff only       # fast-forward only\n"
> +                               "\n"
> +                               "You can replace \"git config\" with \"git config --global\" to set a default\n"
> +                               "preference for all repositories.\n"
> +                               "If unsure, run \"git pull --merge\".\n"
> +                               "Read \"git pull --help\" for more information."
> +                               ));
> +               }
>         }
>
>         if (opt_rebase) {
> diff --git a/t/t5520-pull.sh b/t/t5520-pull.sh
> index 9fae07cdfa..fdd1f79b06 100755
> --- a/t/t5520-pull.sh
> +++ b/t/t5520-pull.sh
> @@ -819,4 +819,66 @@ test_expect_success 'git pull --rebase against local branch' '
>         test_cmp expect file2
>  '
>
> +test_expect_success 'git pull fast-forward (ff-only)' '
> +       test_when_finished "git checkout master && git branch -D other test" &&
> +       test_config pull.ff only &&
> +       git checkout -b other master &&
> +       >new &&
> +       git add new &&
> +       git commit -m new &&
> +       git checkout -b test -t other &&
> +       git reset --hard master &&
> +       git pull
> +'
> +
> +test_expect_success 'git pull non-fast-forward (ff-only)' '
> +       test_when_finished "git checkout master && git branch -D other test" &&
> +       test_config pull.ff only &&
> +       git checkout -b other master^ &&
> +       >new &&
> +       git add new &&
> +       git commit -m new &&
> +       git checkout -b test -t other &&
> +       git reset --hard master &&
> +       test_must_fail git pull
> +'
> +
> +test_expect_failure 'git pull non-fast-forward with merge (ff-only)' '
> +       test_when_finished "git checkout master && git branch -D other test" &&
> +       test_config pull.ff only &&
> +       git checkout -b other master^ &&
> +       >new &&
> +       git add new &&
> +       git commit -m new &&
> +       git checkout -b test -t other &&
> +       git reset --hard master &&
> +       git pull --no-rebase

Do you mean `git pull --merge`?


> +'
> +
> +test_expect_success 'git pull non-fast-forward with rebase (ff-only)' '
> +       test_when_finished "git checkout master && git branch -D other test" &&
> +       test_config pull.ff only &&
> +       git checkout -b other master^ &&
> +       >new &&
> +       git add new &&
> +       git commit -m new &&
> +       git checkout -b test -t other &&
> +       git reset --hard master &&
> +       git pull --rebase
> +'
> +
> +test_expect_success 'git pull non-fast-forward error message' '
> +       test_when_finished "git checkout master && git branch -D other test" &&
> +       test_config pull.ff only &&
> +       git checkout -b other master^ &&
> +       >new &&
> +       git add new &&
> +       git commit -m new &&
> +       git checkout -b test -t other &&
> +       git reset --hard master &&
> +       test_must_fail git pull 2> error &&
> +       cat error &&
> +       grep -q "The pull was not fast-forward" error
> +'
> +
>  test_done
> --
> 2.29.2