rebase: fully ignore rebase.autoSquash without -i

Setting the rebase.autoSquash config variable to true implies a couple
of restrictions: it prevents preemptive fast-forwarding and it triggers
conflicts with apply backend options. However, it only actually results
in auto-squashing when combined with the --interactive (or -i) option,
due to code in run_specific_rebase() that disables auto-squashing unless
the REBASE_INTERACTIVE_EXPLICIT flag is set.

Doing autosquashing for rebase.autoSquash without --interactive would be
problematic in terms of backward compatibility, but conversely, there is
no need for the aforementioned restrictions without --interactive.

So drop the options.config_autosquash check from the conditions for
clearing allow_preemptive_ff, as the case where it is combined with
--interactive is already covered by the REBASE_INTERACTIVE_EXPLICIT
flag check above it.

Also drop the "apply options are incompatible with rebase.autoSquash"
error, because it is unreachable if it is restricted to --interactive,
as apply options already cause an error when used with --interactive.
Drop the tests for the error from t3422-rebase-incompatible-options.sh,
which has separate tests for the conflicts of --interactive with apply
options.

When neither --autosquash nor --no-autosquash are given, only set
options.autosquash to true if rebase.autosquash is combined with
--interactive.

Don't initialize options.config_autosquash to -1, as there is no need to
distinguish between rebase.autoSquash being unset or explicitly set to
false.

Finally, amend the rebase.autoSquash documentation to say it only
affects interactive mode.

Signed-off-by: Andy Koppe <andy.koppe@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config/rebase.txt

@@ -9,7 +9,9 @@ rebase.stat::
 	rebase. False by default.
 
 rebase.autoSquash::
-	If set to true enable `--autosquash` option by default.
+	If set to true, enable the `--autosquash` option of
+	linkgit:git-rebase[1] by default for interactive mode.
+	This can be overridden with the `--no-autosquash` option.
 
 rebase.autoStash::
 	When set to true, automatically create a temporary stash entry

builtin/rebase.c

@@ -149,7 +149,6 @@ struct rebase_options {
 		.reapply_cherry_picks = -1,             \
 		.allow_empty_message = 1,               \
 		.autosquash = -1,                       \
-		.config_autosquash = -1,                \
 		.rebase_merges = -1,                    \
 		.config_rebase_merges = -1,             \
 		.update_refs = -1,                      \
@@ -1405,7 +1404,6 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 	if ((options.flags & REBASE_INTERACTIVE_EXPLICIT) ||
 	    (options.action != ACTION_NONE) ||
 	    (options.exec.nr > 0) ||
-	    (options.autosquash == -1 && options.config_autosquash == 1) ||
 	    options.autosquash == 1) {
 		allow_preemptive_ff = 0;
 	}
@@ -1508,8 +1506,6 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 			if (is_merge(&options))
 				die(_("apply options and merge options "
 					  "cannot be used together"));
-			else if (options.autosquash == -1 && options.config_autosquash == 1)
-				die(_("apply options are incompatible with rebase.autoSquash.  Consider adding --no-autosquash"));
 			else if (options.rebase_merges == -1 && options.config_rebase_merges == 1)
 				die(_("apply options are incompatible with rebase.rebaseMerges.  Consider adding --no-rebase-merges"));
 			else if (options.update_refs == -1 && options.config_update_refs == 1)
@@ -1529,10 +1525,13 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 	options.rebase_merges = (options.rebase_merges >= 0) ? options.rebase_merges :
 				((options.config_rebase_merges >= 0) ? options.config_rebase_merges : 0);
 
-	if (options.autosquash == 1)
+	if (options.autosquash == 1) {
 		imply_merge(&options, "--autosquash");
-	options.autosquash = (options.autosquash >= 0) ? options.autosquash :
+	} else if (options.autosquash == -1) {
-			     ((options.config_autosquash >= 0) ? options.config_autosquash : 0);
+		options.autosquash =
+			options.config_autosquash &&
+			(options.flags & REBASE_INTERACTIVE_EXPLICIT);
+	}
 
 	if (options.type == REBASE_UNSPECIFIED) {
 		if (!strcmp(options.default_backend, "merge"))

t/t3422-rebase-incompatible-options.sh

@@ -100,12 +100,6 @@ test_rebase_am_only () {
 		test_must_fail git rebase $opt --root A
 	"
 
-	test_expect_success "$opt incompatible with rebase.autosquash" "
-		git checkout B^0 &&
-		test_must_fail git -c rebase.autosquash=true rebase $opt A 2>err &&
-		grep -e --no-autosquash err
-	"
-
 	test_expect_success "$opt incompatible with rebase.rebaseMerges" "
 		git checkout B^0 &&
 		test_must_fail git -c rebase.rebaseMerges=true rebase $opt A 2>err &&
@@ -118,12 +112,6 @@ test_rebase_am_only () {
 		grep -e --no-update-refs err
 	"
 
-	test_expect_success "$opt okay with overridden rebase.autosquash" "
-		test_when_finished \"git reset --hard B^0\" &&
-		git checkout B^0 &&
-		git -c rebase.autosquash=true rebase --no-autosquash $opt A
-	"
-
 	test_expect_success "$opt okay with overridden rebase.rebaseMerges" "
 		test_when_finished \"git reset --hard B^0\" &&
 		git checkout B^0 &&