[PATCH v3 2/3] negative-refspec: fix segfault on : refspec

["Nipunn Koorapati via GitGitGadget" <gitgitgadget@gmail.com>]

From: Nipunn Koorapati <nipunn@dropbox.com>

The logic added to check for negative pathspec match by c0192df630
(refspec: add support for negative refspecs, 2020-09-30) looks at
refspec->src assuming it is never NULL, however when
remote.origin.push is set to ":", then refspec->src is NULL,
causing a segfault within strcmp

Tell git to handle matching refspec by adding the needle to the
set of positively matched refspecs, since matching ":" refspecs
match anything as src.

Added testing for matching refspec pushes fetch-negative-refspec
both individually and in combination with a negative refspec

Signed-off-by: Nipunn Koorapati <nipunn@dropbox.com>
---
 remote.c                          | 10 +++++++---
 t/t5582-fetch-negative-refspec.sh | 22 ++++++++++++++++++++++
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/remote.c b/remote.c
index 9f2450cb51b..7323694b163 100644
--- a/remote.c
+++ b/remote.c
@@ -751,9 +751,13 @@ static int query_matches_negative_refspec(struct refspec *rs, struct refspec_ite
 
 			if (match_name_with_pattern(key, needle, value, &expn_name))
 				string_list_append_nodup(&reversed, expn_name);
-		} else {
-			if (!strcmp(needle, refspec->src))
-				string_list_append(&reversed, refspec->src);
+		} else if (refspec->matching) {
+			/* For the special matching refspec, any query should match */
+			string_list_append(&reversed, needle);
+		} else if (!refspec->src) {
+			BUG("refspec->src should not be null here");
+		} else if (!strcmp(needle, refspec->src)) {
+			string_list_append(&reversed, refspec->src);
 		}
 	}
 
diff --git a/t/t5582-fetch-negative-refspec.sh b/t/t5582-fetch-negative-refspec.sh
index 8c61e28fec8..30209e98a62 100755
--- a/t/t5582-fetch-negative-refspec.sh
+++ b/t/t5582-fetch-negative-refspec.sh
@@ -186,4 +186,26 @@ test_expect_success "fetch --prune with negative refspec" '
 	)
 '
 
+test_expect_success "push with matching ':' refspec" '
+	test_config -C two remote.one.push : &&
+	# Fails w/ tip behind counterpart - but should not segfault
+	test_must_fail git -C two push one
+'
+
+test_expect_success "push with matching '+:' refspec" '
+	test_config -C two remote.one.push +: &&
+	# Fails w/ tip behind counterpart - but should not segfault
+	test_must_fail git -C two push one
+'
+
+test_expect_success "push with matching and negative refspec" '
+	test_config -C two --add remote.one.push : &&
+	# Fails to push master w/ tip behind counterpart
+	test_must_fail git -C two push one &&
+
+	# If master is in negative refspec, then the command will succeed
+	test_config -C two --add remote.one.push ^refs/heads/master &&
+	git -C two push one
+'
+
 test_done
-- 
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