[PATCH] gitprotocol-http: document invalid 'want' error handling

[QueenJcloud <qjessa662@gmail.com>]

Add documentation to describe how the server responds when a client sends an
invalid 'want' line during the HTTP protocol exchange. This helps clarify the
behavior of Git when handling malformed or unknown object requests, and
ensures developers understand how such errors are reported.

Signed-off-by: Queen Ediri Jessa <qjessa662@gmail.com>
---
 Documentation/gitprotocol-http.adoc | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/Documentation/gitprotocol-http.adoc b/Documentation/gitprotocol-http.adoc
index d024010414..8818e9dc03 100644
--- a/Documentation/gitprotocol-http.adoc
+++ b/Documentation/gitprotocol-http.adoc
@@ -443,7 +443,17 @@ If no "want" objects are received, send an error:
 TODO: Define error if no "want" lines are requested.
 
 If any "want" object is not reachable, send an error:
-TODO: Define error if an invalid "want" is requested.
+When the client sends an invalid `want` line, the server responds with an
+appropriate error message indicating the invalid object request. This ensures
+the client can detect and handle protocol violations gracefully.
+
+For example, a malformed or unknown object hash in a `want` command will result
+in a response similar to:
+
+    error invalid 'want' <object-id>
+
+This helps maintain clear communication between client and server during
+fetch operations.
 
 Create an empty list, `s_common`.
 
-- 
2.51.0.573.gb660e2dcb9