verify_filename(): handle backslashes in "wildcards are pathspecs" rule

Commit 28fcc0b71a (pathspec: avoid the need of "--" when wildcard is
used, 2015-05-02) allowed:

  git rev-parse '*.c'

without the double-dash. But the rule it uses to check for wildcards
actually looks for any glob special. This is overly liberal, as it means
that a pattern that doesn't actually do any wildcard matching, like
"a\b", will be considered a pathspec.

If you do have such a file on disk, that's presumably what you wanted.
But if you don't, the results are confusing: rather than say "there's no
such path a\b", we'll quietly accept it as a pathspec which very likely
matches nothing (or at least not what you intended). Likewise, looking
for path "a\*b" doesn't expand the search at all; it would only find a
single entry, "a*b".

This commit switches the rule to trigger only when glob metacharacters
would expand the search, meaning both of those cases will now report an
error (you can still disambiguate using "--", of course; we're just
tightening the DWIM heuristic).

Note that we didn't test the original feature in 28fcc0b71a at all. So
this patch not only tests for these corner cases, but also adds a
regression test for the existing behavior.

Reported-by: David Burström <davidburstrom@spotify.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/t/t1506-rev-parse-diagnosis.sh b/t/t1506-rev-parse-diagnosis.sh
index 624d0a588f..2c2bcb024f 100755
--- a/t/t1506-rev-parse-diagnosis.sh
+++ b/t/t1506-rev-parse-diagnosis.sh
@@ -222,4 +222,18 @@ test_expect_success 'reject Nth ancestor if N is too high' '
 	test_must_fail git rev-parse HEAD~100000000000000000000000000000000
 '
 
+test_expect_success 'pathspecs with wildcards are not ambiguous' '
+	echo "*.c" >expect &&
+	git rev-parse "*.c" >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'backslash does not trigger wildcard rule' '
+	test_must_fail git rev-parse "foo\\bar"
+'
+
+test_expect_success 'escaped char does not trigger wildcard rule' '
+	test_must_fail git rev-parse "foo\\*bar"
+'
+
 test_done