ident: reject all-crud ident name

An ident name consisting of only "crud" characters (like
whitespace or punctuation) is effectively the same as an
empty one, because our strbuf_addstr_without_crud() will
remove those characters.

We reject an empty name when formatting a strict ident, but
don't notice an all-crud one because our check happens
before the crud-removal step.

We could skip past the crud before checking for an empty
name, but let's make it a separate code path, for two
reasons. One is that we can give a more specific error
message. And two is that unlike a blank name, we probably
don't want to kick in the fallback-to-username behavior.

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

ident.c

@@ -203,6 +203,15 @@ static int crud(unsigned char c)
 		c == '\'';
 }
 
+static int has_non_crud(const char *str)
+{
+	for (; *str; str++) {
+		if (!crud(*str))
+			return 1;
+	}
+	return 0;
+}
+
 /*
  * Copy over a string to the destination, but avoid special
  * characters ('\n', '<' and '>') and remove crud at the end
@@ -389,6 +398,8 @@ const char *fmt_ident(const char *name, const char *email,
 			pw = xgetpwuid_self(NULL);
 			name = pw->pw_name;
 		}
+		if (strict && !has_non_crud(name))
+			die(_("name consists only of disallowed characters: %s"), name);
 	}
 
 	strbuf_reset(&ident);

t/t7518-ident-corner-cases.sh

@@ -17,4 +17,9 @@ test_expect_success 'empty name and missing email' '
 	)
 '
 
+test_expect_success 'commit rejects all-crud name' '
+	test_must_fail env GIT_AUTHOR_NAME=" .;<>" \
+		git commit --allow-empty -m foo
+'
+
 test_done