correct usage help string for git-hash-object

The usage string is corrected to make it fit in 80 columns and to make it
unequivocal about what options can be used with --stdin-paths.

Signed-off-by: Dmitry Potapov <dpotapov@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-hash-object.txt

@@ -8,7 +8,9 @@ git-hash-object - Compute object ID and optionally creates a blob from a file
 
 SYNOPSIS
 --------
-'git hash-object' [-t <type>] [-w] [--stdin | --stdin-paths] [--] <file>...
+[verse]
+'git hash-object' [-t <type>] [-w] [--stdin] [--] <file>...
+'git hash-object' [-t <type>] [-w] --stdin-paths < <list-of-paths>
 
 DESCRIPTION
 -----------

hash-object.c

@@ -50,7 +50,8 @@ static void hash_stdin_paths(const char *type, int write_objects)
 }
 
 static const char hash_object_usage[] =
-"git hash-object [ [-t <type>] [-w] [--stdin] <file>... | --stdin-paths < <list-of-paths> ]";
+"git hash-object [-t <type>] [-w] [--stdin] [--] <file>...\n"
+"   or: git hash-object  --stdin-paths < <list-of-paths>";
 
 int main(int argc, char **argv)
 {