docs: clarify git-rev-list(1) --filter behavior

When using the --filter option for git-rev-list(1), objects that are
explicitly provided ignore filters and are always printed unless the
--filter-provided-objects option is also specified. Clarify this
behavior in the documentation.

Signed-off-by: Justin Tobler <jltobler@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/rev-list-options.adoc

diff --git a/Documentation/rev-list-options.adoc b/Documentation/rev-list-options.adoc
index d9665d8..453ec59 100644
--- a/Documentation/rev-list-options.adoc
+++ b/Documentation/rev-list-options.adoc
@@ -983,7 +983,9 @@
 is the same as 'blob:limit=1024'.
 +
 The form `--filter=object:type=(tag|commit|tree|blob)` omits all objects
-which are not of the requested type.
+which are not of the requested type. Note that explicitly provided objects
+ignore filters and are always printed unless `--filter-provided-objects` is
+also specified.
 +
 The form `--filter=sparse:oid=<blob-ish>` uses a sparse-checkout
 specification contained in the blob (or blob-expression) _<blob-ish>_