[PATCH v4 1/9] rebase: mark --update-refs as requiring the merge backend

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

From: Elijah Newren <newren@gmail.com>

--update-refs is built in terms of the sequencer, which requires the
merge backend.  It was already marked as incompatible with the apply
backend in the git-rebase manual, but the code didn't check for this
incompatibility and warn the user.  Check and error now.

While at it, fix a typo in t3422...and fix some misleading wording
(most options which used to be am-specific have since been implemented
in the merge backend as well).

Signed-off-by: Elijah Newren <newren@gmail.com>
---
 Documentation/git-rebase.txt           |  2 ++
 builtin/rebase.c                       |  3 +++
 t/t3422-rebase-incompatible-options.sh | 15 ++++++++++-----
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index d811c1cf443..6490bc96a15 100644
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -630,6 +630,8 @@ start would be overridden by the presence of
 +
 If the configuration variable `rebase.updateRefs` is set, then this option
 can be used to override and disable this setting.
++
+See also INCOMPATIBLE OPTIONS below.
 
 INCOMPATIBLE OPTIONS
 --------------------
diff --git a/builtin/rebase.c b/builtin/rebase.c
index a26cc0cfdb5..c111b89e137 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -1492,6 +1492,9 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		}
 	}
 
+	if (options.update_refs)
+		imply_merge(&options, "--update-refs");
+
 	if (options.type == REBASE_UNSPECIFIED) {
 		if (!strcmp(options.default_backend, "merge"))
 			imply_merge(&options, "--merge");
diff --git a/t/t3422-rebase-incompatible-options.sh b/t/t3422-rebase-incompatible-options.sh
index 6dabb05a2ad..9da39cd91c2 100755
--- a/t/t3422-rebase-incompatible-options.sh
+++ b/t/t3422-rebase-incompatible-options.sh
@@ -25,11 +25,11 @@ test_expect_success 'setup' '
 '
 
 #
-# Rebase has lots of useful options like --whitepsace=fix, which are
-# actually all built in terms of flags to git-am.  Since neither
-# --merge nor --interactive (nor any options that imply those two) use
-# git-am, using them together will result in flags like --whitespace=fix
-# being ignored.  Make sure rebase warns the user and aborts instead.
+# Rebase has a couple options which are specific to the apply backend,
+# and several options which are specific to the merge backend.  Flags
+# from the different sets cannot work together, and we do not want to
+# just ignore one of the sets of flags.  Make sure rebase warns the
+# user and aborts instead.
 #
 
 test_rebase_am_only () {
@@ -60,6 +60,11 @@ test_rebase_am_only () {
 		test_must_fail git rebase $opt --exec 'true' A
 	"
 
+	test_expect_success "$opt incompatible with --update-refs" "
+		git checkout B^0 &&
+		test_must_fail git rebase $opt --update-refs A
+	"
+
 }
 
 test_rebase_am_only --whitespace=fix
-- 
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