Walk a path on the blob page from any commit the id names

With both an id and a path the blob page handed back the raw object
the id named, so a commit id gave the commit text itself, while the
plain page looked the path up in that commit's tree. A tag is peeled
to its commit on the way, and the README example of a pinned commit
now uses a form the request checks accept.

1 file changed, 15 insertions, 0 deletions

diff --git a/tests/t0303-robustness.sh b/tests/t0303-robustness.sh
index 73c2ca5..5bdb060 100755
--- a/tests/t0303-robustness.sh
+++ b/tests/t0303-robustness.sh
@@ -246,6 +246,21 @@ test_expect_success 'the blob page reads a file through an annotated tag' '
 	test_cmp want body
 '
 
+# The plain page walks a path out of whatever commit the id names, and the
+# blob page used to answer such a request with the raw commit object.
+test_expect_success 'the blob page walks a path out of the commit or tag the id names' '
+	tip=$(git -C repos/rob rev-parse HEAD) &&
+	robq "url=rob/blob/file-1&id=$tip" >tmp &&
+	strip_headers <tmp >body &&
+	test_cmp want body &&
+	tag=$(git -C repos/rob rev-parse ann) &&
+	robq "url=rob/blob/file-1&id=$tag" >tmp &&
+	strip_headers <tmp >body &&
+	test_cmp want body &&
+	robq "url=rob/blob/missing&id=$tip" >tmp &&
+	grep "^Status: 404" tmp
+'
+
 test_expect_success 'the commit page shows a message whole when text follows its trailers' '
 	(
 		cd repos/rob &&