[PATCH 3/3] get_sha1: don't die() on bogus search strings

[Jeff King <peff@peff.net>]

The get_sha1() function generally returns an error code
rather than dying, and we sometimes speculatively call it
with something that may be a revision or a pathspec, in
order to see which one it might be.

If it sees a bogus ":/" search string, though, it complains,
without giving the caller the opportunity to recover. We can
demonstrate this in t6133 by looking for ":/*.t", which
should mean "*.t at the root of the tree", but instead dies
because of the invalid regex (the "*" has nothing to operate
on).

We can fix this by returning an error rather than calling
die(). Unfortunately, the tradeoff is that the error message
is slightly worse in cases where we _do_ know we have a rev.
E.g., running "git log ':/*.t' --" before yielded:

  fatal: Invalid search pattern: *.t

and now we get only:

  fatal: bad revision ':/*.t'

There's not a simple way to fix this short of passing a
"quiet" flag all the way through the get_sha1() stack.

Signed-off-by: Jeff King <peff@peff.net>
---
To be honest, I'm not sure this is worth it. Part of me wants to say
that get_sha1() is simply wrong for dying. And it is, but given how
infrequently this would come up, it's perhaps a practical tradeoff to
get the more accurate error message.

And while it does confuse ":/*.t", which is obviously a pathspec, that's
just one specific case, that works because of the bogus regex. Something
like ":/foo.*" could mean "find foo.* at the root" or it could mean
"find a commit message with foo followed by anything", and we literally
do not know which.

We're likely to treat that one as a rev (assuming you use "foo" in your
commit messages, but who doesn't?). So you'd need to use "--" in the
general case anyway.

 sha1_name.c                  |  4 ++--
 t/t6133-pathspec-rev-dwim.sh | 10 ++++++++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/sha1_name.c b/sha1_name.c
index 892db21..d61b3b9 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -882,12 +882,12 @@ static int get_sha1_oneline(const char *prefix, unsigned char *sha1,
 
 	if (prefix[0] == '!') {
 		if (prefix[1] != '!')
-			die ("Invalid search pattern: %s", prefix);
+			return -1;
 		prefix++;
 	}
 
 	if (regcomp(&regex, prefix, REG_EXTENDED))
-		die("Invalid search pattern: %s", prefix);
+		return -1;
 
 	for (l = list; l; l = l->next) {
 		l->item->object.flags |= ONELINE_SEEN;
diff --git a/t/t6133-pathspec-rev-dwim.sh b/t/t6133-pathspec-rev-dwim.sh
index 8e5b338..a290ffc 100755
--- a/t/t6133-pathspec-rev-dwim.sh
+++ b/t/t6133-pathspec-rev-dwim.sh
@@ -35,4 +35,14 @@ test_expect_success '@{foo} with metacharacters dwims to rev' '
 	test_cmp expect actual
 '
 
+test_expect_success ':/*.t from a subdir dwims to a pathspec' '
+	mkdir subdir &&
+	(
+		cd subdir &&
+		git log -- ":/*.t" >expect &&
+		git log    ":/*.t" >actual &&
+		test_cmp expect actual
+	)
+'
+
 test_done
-- 
2.7.1.545.gfd1d4e5