On Fri, Jan 24, 2020 at 11:27:35AM -0800, Junio C Hamano wrote:
> Jeff King <peff@xxxxxxxx> writes:
>
> > So everything is working as designed, or at least explainable. But I
> > think there is some room for improvement. A backslash that isn't
> > followed by a glob meta-character _is_ still a meta character (your
> > "a\b" would be globbing for "ab"). But it's useless enough that I think
> > it shouldn't be enough to trigger the "oh, you probably meant this as a
> > pathspec" DWIM rule.
>
> This sounds sensible.
OK, the patch I came up with is below.
> > We _could_ also say "even though this could technically be a pathspec
> > because of its metacharacter, it looks vaguely enough like a
> > path-in-tree revision that we shouldn't guess". That I'm less
> > comfortable with, just because it makes the heuristics even more
> > magical.
>
> Not just it becomes more magical, I am afraid that the code to
> implement such a heuristics would be fragile and become a source of
> unnecessary bugs. Let's not go there.
OK. It does mean that:
git show HEAD:a*
will still quietly produce no output instead of saying "hey, there is no
a* in HEAD". But I think given the lack of bug reports over the years
that this case (and the backslash one I'm fixing) are probably
relatively rare. The backslash one seems a lot more likely, just
because Windows folks may treat it like a path separator (I'm not sure
if that even works, considering its meaning in a glob, but certainly I
can imagine somebody doing so as an experiment and getting confused by
the result).
> I should learn to use "working as designed or at least explainable"
> more often in my responses, by the way. That's quite a useful and
> good phrase ;-)
Perhaps that can be Git's motto. ;)
Anyway, here's the patch. Even though this is rare, I think it's worth
doing. The code is simple and I don't anticipate anybody complaining
about the tightening.
-- >8 --
Subject: 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@xxxxxxxxxxx>
Signed-off-by: Jeff King <peff@xxxxxxxx>
---
setup.c | 23 ++++++++++++++++++++---
t/t1506-rev-parse-diagnosis.sh | 14 ++++++++++++++
2 files changed, 34 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, ":("))
diff --git a/t/t1506-rev-parse-diagnosis.sh b/t/t1506-rev-parse-diagnosis.sh
index 6d951ca015..8a75f37a11 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
--
2.25.0.421.gb74d19af79
