xattr-helper: refactor dump_xattrs to make it a bit more readable

Pull the common qoute chars out into a var and use % with format
strings rather than mixing + in between.

diff --git a/bin/xattr-helper.py b/bin/xattr-helper.py
index 249ea8732a9bbb66087a84c8b6049dfb046ab542..e84d23d5e92d3079eaa89ee06cd346ecaa64ae42 100755 (executable)
--- a/bin/xattr-helper.py
+++ b/bin/xattr-helper.py
@@ -105,6 +105,9 @@ def unquote(s):
 
 def dump_xattrs(file_in, file_out):
        """Dump the xattr data for files in |file_in| to |file_out|"""
+       # NOTE: Always quote backslashes, in order to ensure that they are
+       # not interpreted as quotes when they are processed by unquote.
+       quote_chars = b'\n\r\\\\'
 
        for pathname in file_in.read().split(b'\0'):
                if not pathname:
@@ -114,13 +117,14 @@ def dump_xattrs(file_in, file_out):
                if not attrs:
                        continue
 
-               # NOTE: Always quote backslashes, in order to ensure that they are
-               # not interpreted as quotes when they are processed by unquote.
-               file_out.write(b'# file: ' + quote(pathname, b'\n\r\\\\') + b'\n')
+               file_out.write(b'# file: %s\n' % quote(pathname, quote_chars))
                for attr in attrs:
                        attr = unicode_encode(attr)
-                       file_out.write(quote(attr, b'=\n\r\\\\') + b'="' +
-                               quote(xattr.get(pathname, attr), b'\0\n\r"\\\\') + b'"\n')
+                       value = xattr.get(pathname, attr)
+                       file_out.write(b'%s="%s"\n' % (
+                               quote(attr, b'=' + quote_chars),
+                               quote(value, b'\0"' + quote_chars)))
+
 
 def restore_xattrs(file_in):
        """Read |file_in| and restore xattrs content from it