[PATCH v3 4/8] pull: since --ff-only overrides, handle it first

["Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com>]

From: Elijah Newren <newren@gmail.com>

There are both merge and rebase branches in the logic, and previously
both had to handle fast-forwarding.  Merge handled that implicitly
(because git merge handles it directly), while in rebase it was
explicit.  Given that the --ff-only flag is meant to override any
--rebase or --no-rebase, make the code reflect that by handling
--ff-only before the merge-vs-rebase logic.

It turns out that this also fixes a bug for submodules.  Previously,
when --ff-only was given, the code would run `merge --ff-only` on the
main module, and then run `submodule update --recursive --rebase` on the
submodules.  With this change, we still run `merge --ff-only` on the
main module, but now run `submodule update --recursive --checkout` on
the submodules.  I believe this better reflects the intent of --ff-only
to have it apply to both the main module and the submodules.

(Sidenote: It is somewhat interesting that all merges pass `--checkout`
to submodule update, even when `--no-ff` is specified, meaning that it
will only do fast-forward merges for submodules.  This was discussed in
commit a6d7eb2c7a ("pull: optionally rebase submodules (remote submodule
changes only)", 2017-06-23).  The same limitations apply now as then, so
we are not trying to fix this at this time.)

Signed-off-by: Elijah Newren <newren@gmail.com>
---
 builtin/pull.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/builtin/pull.c b/builtin/pull.c
index d9796604825..1f452020375 100644
--- a/builtin/pull.c
+++ b/builtin/pull.c
@@ -1046,15 +1046,15 @@ int cmd_pull(int argc, const char **argv, const char *prefix)
 
 	can_ff = get_can_ff(&orig_head, &merge_heads.oid[0]);
 
-	if (!can_ff) {
-		if (opt_ff) {
-			if (!strcmp(opt_ff, "--ff-only"))
-				die_ff_impossible();
-		} else {
-			if (rebase_unspecified && opt_verbosity >= 0)
-				show_advice_pull_non_ff();
-		}
+	/* ff-only takes precedence over rebase */
+	if (opt_ff && !strcmp(opt_ff, "--ff-only")) {
+		if (!can_ff)
+			die_ff_impossible();
+		opt_rebase = REBASE_FALSE;
 	}
+	/* If no action specified and we can't fast forward, then warn. */
+	if (!opt_ff && rebase_unspecified && !can_ff)
+		show_advice_pull_non_ff();
 
 	if (opt_rebase) {
 		int ret = 0;
-- 
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