upload-pack.c: allow banning certain object filter(s)

Git clients may ask the server for a partial set of objects, where the
set of objects being requested is refined by one or more object filters.
Server administrators can configure 'git upload-pack' to allow or ban
these filters by setting the 'uploadpack.allowFilter' variable to
'true' or 'false', respectively.

However, administrators using bitmaps may wish to allow certain kinds of
object filters, but ban others. Specifically, they may wish to allow
object filters that can be optimized by the use of bitmaps, while
rejecting other object filters which aren't and represent a perceived
performance degradation (as well as an increased load factor on the
server).

Allow configuring 'git upload-pack' to support object filters on a
case-by-case basis by introducing two new configuration variables:

  - 'uploadpackfilter.allow'
  - 'uploadpackfilter.<kind>.allow'

where '<kind>' may be one of 'blobNone', 'blobLimit', 'tree', and so on.

Setting the second configuration variable for any valid value of
'<kind>' explicitly allows or disallows restricting that kind of object
filter.

If a client requests the object filter <kind> and the respective
configuration value is not set, 'git upload-pack' will default to the
value of 'uploadpackfilter.allow', which itself defaults to 'true' to
maintain backwards compatibility. Note that this differs from
'uploadpack.allowfilter', which controls whether or not the 'filter'
capability is advertised.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/t/t5616-partial-clone.sh b/t/t5616-partial-clone.sh
index 8a27452..1fff4ff 100755
--- a/t/t5616-partial-clone.sh
+++ b/t/t5616-partial-clone.sh
@@ -235,6 +235,30 @@ test_expect_success 'implicitly construct combine: filter with repeated flags' '
 	test_cmp unique_types.expected unique_types.actual
 '
 
+test_expect_success 'upload-pack fails banned object filters' '
+	test_config -C srv.bare uploadpackfilter.blob:none.allow false &&
+	test_must_fail ok=sigpipe git clone --no-checkout --filter=blob:none \
+		"file://$(pwd)/srv.bare" pc3 2>err &&
+	grep "filter '\''blob:none'\'' not supported" err
+'
+
+test_expect_success 'upload-pack fails banned combine object filters' '
+	test_config -C srv.bare uploadpackfilter.allow false &&
+	test_config -C srv.bare uploadpackfilter.combine.allow true &&
+	test_config -C srv.bare uploadpackfilter.tree.allow true &&
+	test_config -C srv.bare uploadpackfilter.blob:none.allow false &&
+	test_must_fail ok=sigpipe git clone --no-checkout --filter=tree:1 \
+		--filter=blob:none "file://$(pwd)/srv.bare" pc3 2>err &&
+	grep "filter '\''blob:none'\'' not supported" err
+'
+
+test_expect_success 'upload-pack fails banned object filters with fallback' '
+	test_config -C srv.bare uploadpackfilter.allow false &&
+	test_must_fail ok=sigpipe git clone --no-checkout --filter=blob:none \
+		"file://$(pwd)/srv.bare" pc3 2>err &&
+	grep "filter '\''blob:none'\'' not supported" err
+'
+
 test_expect_success 'partial clone fetches blobs pointed to by refs even if normally filtered out' '
 	rm -rf src dst &&
 	git init src &&