[PATCH 1/2] sha1_name: don't trigger detailed diagnosis for file arguments

[Matthieu Moy <Matthieu.Moy@imag.fr>]

diagnose_invalid_sha1_path is normally meant to be called to diagnose
<treeish>:<pathname> when <pathname> does not exist in <treeish>.
However, the current code may call it if <treeish>:<pathname> is invalid
(which triggers another call with only_to_die == 1), but for another
reason. This happens when calling e.g.

  git log existing-file HEAD:existing-file

(because existing-file is a file and not a revision, the next arguments
are assumed to be files too), leading to incorrect message like
"existing-file does not exist in HEAD".

Check that the search for <pathname> in <treeish> fails before triggering
the diagnosis.

Bug report and code fix by: Junio C Hamano <gitster@pobox.com>
Test by: Matthieu Moy <Matthieu.Moy@imag.fr>

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
---

This patch is very simple and should be rather uncontroversial.

 sha1_name.c                    |  2 +-
 t/t1506-rev-parse-diagnosis.sh | 11 +++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/sha1_name.c b/sha1_name.c
index c633113..5d81ea0 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -1127,7 +1127,7 @@ int get_sha1_with_context_1(const char *name, unsigned char *sha1,
 			if (new_filename)
 				filename = new_filename;
 			ret = get_tree_entry(tree_sha1, filename, sha1, &oc->mode);
-			if (only_to_die) {
+			if (ret && only_to_die) {
 				diagnose_invalid_sha1_path(prefix, filename,
 							   tree_sha1, object_name);
 				free(object_name);
diff --git a/t/t1506-rev-parse-diagnosis.sh b/t/t1506-rev-parse-diagnosis.sh
index 0843a1c..4a39ac5 100755
--- a/t/t1506-rev-parse-diagnosis.sh
+++ b/t/t1506-rev-parse-diagnosis.sh
@@ -171,4 +171,15 @@ test_expect_success 'relative path when startup_info is NULL' '
 	grep "BUG: startup_info struct is not initialized." error
 '
 
+test_expect_success '<commit>:file correctly diagnosed after a pathname' '
+	test_must_fail git rev-parse file.txt HEAD:file.txt 1>actual 2>error &&
+	test_i18ngrep ! "exists on disk" error &&
+	test_i18ngrep "unknown revision or path not in the working tree" error &&
+	cat >expect <<EOF &&
+file.txt
+HEAD:file.txt
+EOF
+	test_cmp expect actual
+'
+
 test_done
-- 
1.7.11.rc0.57.g84a04c7