[PATCH] sideband: skip unrecognized allowControlCharacters keywords

["Thomas Bachem via GitGitGadget" <gitgitgadget@gmail.com>]

From: Thomas Bachem <mail@thomasbachem.com>

Since 128914438a (sideband: add options to allow more control
sequences to be passed through, 2026-03-05), the value of
sideband.allowControlCharacters is a comma-separated list of
keywords. When the parser meets a keyword it does not know, it warns
but stays on that keyword, so the warning repeats forever.

As the setting is read whenever a transport is set up, a typo like
"colour", a list written as "color, cursor" with a space, or a
keyword that only a newer version of Git knows is enough to make
every fetch, push, clone and ls-remote hang this way.

Move on to the next keyword after the warning, and name only the
unrecognized keyword in it, not the rest of the list.

Assisted-by: Claude Opus 5.5
Signed-off-by: Thomas Bachem <mail@thomasbachem.com>
---
    sideband: skip unrecognized allowControlCharacters keywords

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2261%2Fthomasbachem%2Fsideband-control-characters-loop-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2261/thomasbachem/sideband-control-characters-loop-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/2261

 sideband.c                          | 19 ++++++++++++-------
 t/t5409-colorize-remote-messages.sh | 25 +++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/sideband.c b/sideband.c
index 374187402e..ed6840bf89 100644
--- a/sideband.c
+++ b/sideband.c
@@ -62,18 +62,23 @@ int sideband_allow_control_characters_config(const char *var, const char *value)
 
 	allow_control_characters = ALLOW_NO_CONTROL_CHARACTERS;
 	while (*value) {
-		if (skip_prefix_in_csv(value, "color", &value))
+		if (skip_prefix_in_csv(value, "color", &value)) {
 			allow_control_characters |= ALLOW_ANSI_COLOR_SEQUENCES;
-		else if (skip_prefix_in_csv(value, "cursor", &value))
+		} else if (skip_prefix_in_csv(value, "cursor", &value)) {
 			allow_control_characters |= ALLOW_ANSI_CURSOR_MOVEMENTS;
-		else if (skip_prefix_in_csv(value, "erase", &value))
+		} else if (skip_prefix_in_csv(value, "erase", &value)) {
 			allow_control_characters |= ALLOW_ANSI_ERASE;
-		else if (skip_prefix_in_csv(value, "true", &value))
+		} else if (skip_prefix_in_csv(value, "true", &value)) {
 			allow_control_characters = ALLOW_ALL_CONTROL_CHARACTERS;
-		else if (skip_prefix_in_csv(value, "false", &value))
+		} else if (skip_prefix_in_csv(value, "false", &value)) {
 			allow_control_characters = ALLOW_NO_CONTROL_CHARACTERS;
-		else
-			warning(_("unrecognized value for '%s': '%s'"), var, value);
+		} else {
+			const char *end = strchrnul(value, ',');
+
+			warning(_("unrecognized value for '%s': '%.*s'"),
+				var, (int)(end - value), value);
+			value = end + !!*end;
+		}
 	}
 	return 0;
 }
diff --git a/t/t5409-colorize-remote-messages.sh b/t/t5409-colorize-remote-messages.sh
index 5da8b0ad64..6117579eb1 100755
--- a/t/t5409-colorize-remote-messages.sh
+++ b/t/t5409-colorize-remote-messages.sh
@@ -190,4 +190,29 @@ test_expect_success 'allow all control sequences for a specific URL' '
 	test_grep ! "\\^\\[\\[K" decoded
 '
 
+test_expect_success 'unrecognized keywords in allowControlCharacters are skipped' '
+	write_script .git/eraser <<-\EOF &&
+	printf "error: Ohai!\\r\\033[K" >&2
+	exec "$@"
+	EOF
+	test_config_global uploadPack.packObjectsHook ./eraser &&
+	test_commit unrecognized-keyword &&
+
+	# Cap the output, so that a parser stuck on the unrecognized
+	# keyword fails the test instead of warning forever.
+	git -c sideband.allowControlCharacters=bogus,erase \
+		ls-remote . 2>&1 >/dev/null |
+	head -n 2 >warnings &&
+	test_line_count = 1 warnings &&
+	test_grep "allowcontrolcharacters.: .bogus.$" warnings &&
+
+	rm -rf throw-away &&
+	git -c sideband.allowControlCharacters=bogus,erase \
+		clone --no-local . throw-away 2>stderr &&
+	test_decode_color <stderr >color-decoded &&
+	test_decode_csi <color-decoded >decoded &&
+	test_grep "CSI \\[K" decoded &&
+	test_grep ! "\\^\\[\\[K" decoded
+'
+
 test_done

base-commit: 6de20f6092dcf9bdb1c8efe03db4b70c82b423dd
-- 
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