[PATCH v2 5/7] rebase: don't have loop over "struct strvec" depend on signed "nr"

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

As in the preceding commit, prepare for the "nr" member of "struct
strvec" changing from an "int" to a "size_t".

Let's change this code added in f57696802c3 (rebase: really just
passthru the `git am` options, 2018-11-14) so that it won't cause a
bug if the "i" variable here is updated to be a "size_t" instead of an
"int".

The reason it would be buggy is because this for-loop relied on
"counting down" from nr-1 to 0, we'll then decrement the variable one
last time, so a value of -1 indicates that we've visited all
elements. Since we're looking for a needle in the haystack having
looked at all the hay means that the needle isn't there.

Let's replace this with simpler code that loops overthe "struct
strvec" and checks the current needle is "-q", if it isn't and we're
doing a merge we die, otherwise we do a "REBASE_APPLY".

We've been able to simplify this code since 8295ed690bf (rebase: make
the backend configurable via config setting, 2020-02-15) when we
stopped using this for anything except this one check, so let's do
that and move the check into the loop itself.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 builtin/rebase.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/builtin/rebase.c b/builtin/rebase.c
index 27669880918..dcd897fda9c 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -1750,16 +1750,14 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 
 	if (options.git_am_opts.nr || options.type == REBASE_APPLY) {
 		/* all am options except -q are compatible only with --apply */
-		for (i = options.git_am_opts.nr - 1; i >= 0; i--)
-			if (strcmp(options.git_am_opts.v[i], "-q"))
-				break;
-
-		if (i >= 0) {
-			if (is_merge(&options))
-				die(_("cannot combine apply options with "
-				      "merge options"));
-			else
+		for (i = 0; i < options.git_am_opts.nr; i++) {
+			if (strcmp(options.git_am_opts.v[i], "-q")) {
+				if (is_merge(&options))
+					die(_("cannot combine apply options with "
+					      "merge options"));
 				options.type = REBASE_APPLY;
+				break;
+			}
 		}
 	}
 
-- 
2.33.0.998.ga4d44345d43