Re: [PATCH RFC] rebase: respect --ff-only option

On Mon, Jul 5, 2021 at 2:53 AM Phillip Wood [off-list ref] wrote:

On 05/07/2021 05:45, Alex Henrie wrote:

quoted

index 12f093121d..b88f0cbcca 100644

--- a/builtin/rebase.c
+++ b/builtin/rebase.c

@@ -1345,12 +1349,14 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
                       N_("ignore changes in whitespace")),
              OPT_PASSTHRU_ARGV(0, "whitespace", &options.git_am_opts,
                                N_("action"), N_("passed to 'git apply'"), 0),
-             OPT_BIT('f', "force-rebase", &options.flags,
-                     N_("cherry-pick all commits, even if unchanged"),
-                     REBASE_FORCE),
-             OPT_BIT(0, "no-ff", &options.flags,
-                     N_("cherry-pick all commits, even if unchanged"),
-                     REBASE_FORCE),
+             OPT_SET_INT_F('f', "force-rebase", &options.fast_forward,
+                           N_("cherry-pick all commits, even if unchanged"),
+                           FF_NO, PARSE_OPT_NONEG),

Why does this change rebase to start rejecting --no-force-rebase? This
is the sort of behavior change that deserves a mention in the commit
message.

That was accidental, sorry. I copied and pasted option code from
another place without paying attention to the PARSE_OPT_NONEG.

quoted

+             OPT_SET_INT(0, "ff", &options.fast_forward, N_("allow fast-forward"),
+                         FF_ALLOW),

The useful option when rebasing is '--no-ff', now that will no longer
appear in the output of 'git rebase -h'

Yeah, that's a good point.

On Mon, Jul 5, 2021 at 3:36 AM Ævar Arnfjörð Bjarmason [off-list ref] wrote:

On Sun, Jul 04 2021, Alex Henrie wrote:

quoted

+int error_ff_impossible(void)
+{
+     error(_("Not possible to fast-forward, aborting."));
+     return -1;
+}

Here's one, the idiom is just "return error", i.e it itself returns -1.

That would indeed be simpler; thanks for pointing that out.

FWIW I'd consider doing:

        /* earlier, static scope */
        static const char error_ff_impossible = N_("Not possible...");
        /* later, function scope */
            return error(error_ff_impossible);

It's a small difference, but for translators who use the jump-to-source
while translating not having the indirection helps, and in this case
it's just used 3 times...

Wouldn't jump-to-source take the user to the English text in advice.c
either way? How does putting it in a static variable help?

quoted

[...]
      if (parent && parse_commit(parent) < 0)
              /* TRANSLATORS: The first %s will be a "todo" command like

@@ -2764,7 +2769,7 @@ static int populate_opts_cb(const char *key, const char *value, void *data)
      else if (!strcmp(key, "options.record-origin"))
              opts->record_origin = git_config_bool_or_int(key, value, &error_flag);
      else if (!strcmp(key, "options.allow-ff"))
-             opts->allow_ff = git_config_bool_or_int(key, value, &error_flag);
+             opts->fast_forward = git_config_bool_or_int(key, value, &error_flag) ? FF_ALLOW : FF_NO;

Since we're on nits, we try to wrap at 80 characters.

Thanks, I didn't know what the exact cutoff was.

quoted

+test_expect_success "rebase: impossible fast-forward rebase" '
+     test_config rebase.autostash true &&
+     git reset --hard &&
+     echo dirty >>file1 &&
+     (git rebase --ff-only unrelated-onto-branch || true) &&

Never "||" git commands, better as test_might_fail. We don't want to
hide segfaults.

Also thanks for the advice here.

On Mon, Jul 5, 2021 at 10:50 AM Junio C Hamano [off-list ref] wrote:

Phillip Wood [off-list ref] writes:

quoted

Looking at origin/seen:builtin/pull.c we already check if we can
fast-forward and unconditionally merge in that case irrespective of
any '--rebase' option or pull.rebase config. It should be simple for
pull to error out if '--ff-only' is given and we cannot fast-forward.

Excellent.

Even though teaching even more special case on the "git pull" side
makes me feel somewhat dirty, but I think it would be a small price
to pay, and the end result would save an useless fork whose sole
purpose is to make the integration step after fetch fail when "pull"
can easily tell, as you said, that it ought to fail, so overall it
would probably be a net win.

Okay, so it sounds like I should just scrap this patch and try again,
after "pull: cleanup autostash check" is in master, with a patch that
only modifies `git pull` and not `git rebase`. (Unless someone more
experienced wants to take over, which would be fine by me.)

Thanks anyway to Phillip and Ævar: Your feedback will help me write
better patches in the future.

-Alex