signature: don't blow up trying to parse names containing '>'

When trying to find the end of an email, instead of starting at the
beginning of the signature, we start at the end of the name (after the
first '<').

This brings libgit2 more in line with Git's behavior when reading out
existing signatures.

However, note that Git does not allow names like these through the
usual porcelain; instead, it silently strips any '>' characters it
sees.

src/signature.c

@@ -279,7 +279,7 @@ int git_signature__parse(git_signature *sig, const char **buffer_out,
 	if ((name_end = strchr(buffer, '<')) == NULL)
 		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse signature. Cannot find '<' in signature");
 
-	if ((email_end = strchr(buffer, '>')) == NULL)
+	if ((email_end = strchr(name_end, '>')) == NULL)
 		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse signature. Cannot find '>' in signature");
 
 	if (email_end < name_end)

tests/t04-commit.c

@@ -412,6 +412,14 @@ BEGIN_TEST(parse1, "parse the signature line in a commit")
 		1234567890,
 		0);
 
+	TEST_SIGNATURE_PASS(
+		"author A U Thor> <author@example.com> and others 1234567890\n",
+		"author ",
+		"A U Thor>",
+		"author@example.com",
+		1234567890,
+		0);
+
 	TEST_SIGNATURE_FAIL(
 		"committer Vicent Marti tanoku@gmail.com> 123456 -0100 \n",
 		"committer ");