gitannex: speed up the end to end tests with testremote --fast

Run the full "git annex testremote" suite for a single layout mode and
use "testremote --fast" for the rest.

The full suite repeats the same protocol operations across a matrix of
key sizes and chunk configurations, which exercises client side
git-annex behaviour rather than rclone.

cmd/gitannex/e2e_test.go

@@ -247,7 +247,16 @@ func TestEndToEnd(t *testing.T) {
 				"rcloneremotename=MyRcloneRemote", "rcloneprefix="+testingContext.ephemeralRepoDir,
 				"rclonelayout="+string(mode))
 
-			testingContext.runInRepo(t, "git", "annex", "testremote", "MyTestRemote")
+			// Layout modes only vary how object paths are constructed, so
+			// one layout mode gets the full testremote suite for depth. The
+			// rest use --fast, which still exercises every special remote
+			// protocol operation but skips the key size and chunking matrix
+			// that mostly tests git-annex itself.
+			if mode == layoutModeNodir {
+				testingContext.runInRepo(t, "git", "annex", "testremote", "MyTestRemote")
+			} else {
+				testingContext.runInRepo(t, "git", "annex", "testremote", "--fast", "MyTestRemote")
+			}
 		})
 	}
 }