[Outreachy PATCH v2 1/2] t0410: use rev-parse to get the subtree OID

[Dorine Tipo <dorine.a.tipo@gmail.com>]

The 'rev-list stops traversal at missing and promised tree' test gets
the OID of a_dir by piping 'git ls-tree' through grep, head and cut.

The pipeline goes against t/README which says not to pipe the output
of a git command, since only the last command's exit code is kept.
It also silently assumes that the first tree in the ls-tree output is
the one we want, without checking which path it is stored at.
And 'cut -b13-52' also assumes a 40-character SHA-1 name, so under
SHA-256 TREE2 holds an abbreviated OID.

Use 'git rev-parse HEAD:a_dir' instead. It names the directory we are
interested in explicitly and returns the full OID in a single command,
the same way TREE is computed with 'git rev-parse foo^{tree}' just
above.

Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Dorine Tipo <dorine.a.tipo@gmail.com>
---
 t/t0410-partial-clone.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/t/t0410-partial-clone.sh b/t/t0410-partial-clone.sh
index 788e9a1631..a24b663f73 100755
--- a/t/t0410-partial-clone.sh
+++ b/t/t0410-partial-clone.sh
@@ -405,7 +405,7 @@ test_expect_success 'rev-list stops traversal at missing and promised tree' '
 	TREE=$(git -C repo rev-parse foo^{tree}) &&
 
 	# a tree referenced by HEAD^{tree} (tree referenced from tree)
-	TREE2=$(git -C repo ls-tree HEAD^{tree} | grep " tree " | head -1 | cut -b13-52) &&
+	TREE2=$(git -C repo rev-parse HEAD:a_dir) &&
 
 	promise_and_delete "$TREE" &&
 	promise_and_delete "$TREE2" &&
-- 
2.34.1