t: create test harness for 'bundle-uri' command

The previous change allowed for a Git server to advertise the
'bundle-uri' command as a capability based on the
uploadPack.advertiseBundleURIs config option. Create a set of tests that
check that this capability is advertised using 'git ls-remote'.

In order to test this functionality across three protocols (file, git,
and http), create lib-bundle-uri-protocol.sh to generalize the tests,
allowing the other test scripts to set an environment variable and
otherwise inherit the setup and tests from this script.

The tests currently only test that the 'bundle-uri' command is
advertised or not. Other actions will be tested as the Git client learns
to request the 'bundle-uri' command and parse its response.

To help with URI escaping, specifically for file paths with a space in
them, extract a 'sed' invocation from t9199-git-svn-info.sh into a
helper function for use here, too.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/test-lib-functions.sh

@@ -1751,6 +1751,13 @@ test_path_is_hidden () {
 	return 1
 }
 
+# Poor man's URI escaping. Good enough for the test suite whose trash
+# directory has a space in it. See 93c3fcbe4d4 (git-svn: attempt to
+# mimic SVN 1.7 URL canonicalization, 2012-07-28) for prior art.
+test_uri_escape() {
+	sed 's/ /%20/g'
+}
+
 # Check that the given command was invoked as part of the
 # trace2-format trace on stdin.
 #