[PATCH] add: don't write objects with --dry-run

["René Scharfe" <l.s.r@web.de>]

When the option --dry-run/-n is given, "git add" doesn't change the
index, but still writes out new object files.  Only hash the latter
without writing instead to make the run as dry as possible.

Use this opportunity to also make the hash_flags variable unsigned,
to match the index_path() parameter it is used as.

Reported-by: git.mexon@spamgourmet.com
Signed-off-by: René Scharfe <l.s.r@web.de>
---
Am I missing something?  Do we sometimes rely on the written objects
within the "git add --dry-run" command?

 read-cache.c          | 2 +-
 t/t2200-add-update.sh | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/read-cache.c b/read-cache.c
index a78b88a41b..7fcc948077 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -738,7 +738,7 @@ int add_to_index(struct index_state *istate, const char *path, struct stat *st,
 	int intent_only = flags & ADD_CACHE_INTENT;
 	int add_option = (ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE|
 			  (intent_only ? ADD_CACHE_NEW_ONLY : 0));
-	int hash_flags = HASH_WRITE_OBJECT;
+	unsigned hash_flags = pretend ? 0 : HASH_WRITE_OBJECT;
 	struct object_id oid;

 	if (flags & ADD_CACHE_RENORMALIZE)
diff --git a/t/t2200-add-update.sh b/t/t2200-add-update.sh
index 45ca35d60a..94c4cb0672 100755
--- a/t/t2200-add-update.sh
+++ b/t/t2200-add-update.sh
@@ -129,12 +129,15 @@ test_expect_success 'add -n -u should not add but just report' '
 		echo "remove '\''top'\''"
 	) >expect &&
 	before=$(git ls-files -s check top) &&
+	git count-objects -v >objects_before &&
 	echo changed >>check &&
 	rm -f top &&
 	git add -n -u >actual &&
 	after=$(git ls-files -s check top) &&
+	git count-objects -v >objects_after &&

 	test "$before" = "$after" &&
+	test_cmp objects_before objects_after &&
 	test_cmp expect actual

 '
--
2.33.0