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, 20 insertions, 3 deletions

diff --git a/setup.c b/setup.c
index e2a479a64f..12228c0d9c 100644
--- a/setup.c
+++ b/setup.c
@@ -197,9 +197,26 @@ static void NORETURN die_verify_filename(struct repository *r,
  */
 static int looks_like_pathspec(const char *arg)
 {
-	/* anything with a wildcard character */
-	if (!no_wildcard(arg))
-		return 1;
+	const char *p;
+	int escaped = 0;
+
+	/*
+	 * Wildcard characters imply the user is looking to match pathspecs
+	 * that aren't in the filesystem. Note that this doesn't include
+	 * backslash even though it's a glob special; by itself it doesn't
+	 * cause any increase in the match. Likewise ignore backslash-escaped
+	 * wildcard characters.
+	 */
+	for (p = arg; *p; p++) {
+		if (escaped) {
+			escaped = 0;
+		} else if (is_glob_special(*p)) {
+			if (*p == '\\')
+				escaped = 1;
+			else
+				return 1;
+		}
+	}
 
 	/* long-form pathspec magic */
 	if (starts_with(arg, ":("))