grep: fix "--" rev/pathspec disambiguation

If we see "git grep pattern rev -- file" then we apply the
usual rev/pathspec disambiguation rules: any "rev" before
the "--" must be a revision, and we do not need to apply the
verify_non_filename() check.

But there are two bugs here:

  1. We keep a seen_dashdash flag to handle this case, but
     we set it in the same left-to-right pass over the
     arguments in which we parse "rev".

     So when we see "rev", we do not yet know that there is
     a "--", and we mistakenly complain if there is a
     matching file.

     We can fix this by making a preliminary pass over the
     arguments to find the "--", and only then checking the rev
     arguments.

  2. If we can't resolve "rev" but there isn't a dashdash,
     that's OK. We treat it like a path, and complain later
     if it doesn't exist.

     But if there _is_ a dashdash, then we know it must be a
     rev, and should treat it as such, complaining if it
     does not resolve. The current code instead ignores it
     and tries to treat it like a path.

This patch fixes both bugs, and tries to comment the parsing
flow a bit better.

It adds tests that cover the two bugs, but also some related
situations (which already worked, but this confirms that our
fixes did not break anything).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/t/t7810-grep.sh b/t/t7810-grep.sh
index 2c1f7373e6..a6011f9b1d 100755
--- a/t/t7810-grep.sh
+++ b/t/t7810-grep.sh
@@ -982,6 +982,39 @@ test_expect_success 'grep -e -- -- path' '
 	test_cmp expected actual
 '
 
+test_expect_success 'dashdash disambiguates rev as rev' '
+	test_when_finished "rm -f master" &&
+	echo content >master &&
+	echo master:hello.c >expect &&
+	git grep -l o master -- hello.c >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'dashdash disambiguates pathspec as pathspec' '
+	test_when_finished "git rm -f master" &&
+	echo content >master &&
+	git add master &&
+	echo master:content >expect &&
+	git grep o -- master >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'report bogus arg without dashdash' '
+	test_must_fail git grep o does-not-exist
+'
+
+test_expect_success 'report bogus rev with dashdash' '
+	test_must_fail git grep o hello.c --
+'
+
+test_expect_success 'allow non-existent path with dashdash' '
+	# We need a real match so grep exits with success.
+	tree=$(git ls-tree HEAD |
+	       sed s/hello.c/not-in-working-tree/ |
+	       git mktree) &&
+	git grep o "$tree" -- not-in-working-tree
+'
+
 test_expect_success 'grep --no-index pattern -- path' '
 	rm -fr non &&
 	mkdir -p non/git &&