[PATCH 1/2] merge-recursive: prepare for `merge_submodule()` to report errors

["Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>]

From: Johannes Schindelin <johannes.schindelin@gmx.de>

The `merge_submodule()` function returns an integer that indicates
whether the merge was clean (returning 1) or unclean (returning 0).

Like the version in `merge-ort.c`, the version in `merge-recursive.c`
does not report any errors (such as repository corruption) by returning
-1 as of time of writing, even if the callers in `merge-ort.c` are
prepared for exactly such errors.

However, we want to teach (both variants of) the `merge_submodule()`
function that trick: to report errors by returning -1. Therefore,
prepare the caller in `merge-recursive.c` to handle that scenario.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 merge-recursive.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/merge-recursive.c b/merge-recursive.c
index 32e9d6665de..f3132a9ecae 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -1426,13 +1426,14 @@ static int merge_mode_and_contents(struct merge_options *opt,
 			/* FIXME: bug, what if modes didn't match? */
 			result->clean = (merge_status == 0);
 		} else if (S_ISGITLINK(a->mode)) {
-			result->clean = merge_submodule(opt, &result->blob.oid,
-							o->path,
-							&o->oid,
-							&a->oid,
-							&b->oid);
-			if (result->clean < 0)
+			int clean = merge_submodule(opt, &result->blob.oid,
+						    o->path,
+						    &o->oid,
+						    &a->oid,
+						    &b->oid);
+			if (clean < 0)
 				return -1;
+			result->clean = clean;
 		} else if (S_ISLNK(a->mode)) {
 			switch (opt->recursive_variant) {
 			case MERGE_VARIANT_NORMAL:
-- 
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