Add option to ignore UID/GID when comparing file changes

/reviewed-on !2

rdiff_backup/Globals.py

@@ -251,6 +251,10 @@ symlink_perms = None
 # tempfile.tempdir value on remote connections
 remote_tempdir = None
 
+# If set, don't compare uid/gid or uname/gname when comparing
+# two RORPath
+ignore_numerical_ids = None
+
 def get(name):
 	"""Return the value of something in this module"""
 	return globals()[name]

rdiff_backup/Main.py

@@ -71,6 +71,7 @@ def parse_cmdlineoptions(arglist):
 		  "exclude-globbing-filelist-stdin", "exclude-mirror=",
 		  "exclude-other-filesystems", "exclude-regexp=", "exclude-if-present=",
 		  "exclude-special-files", "force", "group-mapping-file=",
+		  "ignore-numerical-ids",
 		  "include=", "include-filelist=", "include-filelist-stdin",
 		  "include-globbing-filelist=",
 		  "include-globbing-filelist-stdin", "include-regexp=",
@@ -136,6 +137,7 @@ def parse_cmdlineoptions(arglist):
 		elif opt == "--always-snapshot-fromfile":
 			with open(arg, 'rb') as fin:
 				Globals.always_snapshot.extend(tuple(line.strip('\n').split('/')) for line in fin.xreadlines())
+		elif opt == "--ignore-numerical-ids": Globals.set("ignore_numerical_ids", 1)
 		elif (opt == "--include" or
 			  opt == "--include-special-files" or
 			  opt == "--include-symbolic-links"):

rdiff_backup/rpath.py

@@ -436,6 +436,7 @@ class RORPath:
 		for key in self.data.keys(): # compare dicts key by key
 			if self.issym() and key in ('uid', 'gid', 'uname', 'gname'):
 				pass # Don't compare gid/uid for symlinks
+			elif key in ('uid', 'gid', 'uname', 'gname') and Globals.ignore_numerical_ids: pass
 			elif key == 'atime' and not Globals.preserve_atime: pass
 			elif key == 'ctime': pass
 			elif key == 'nlink': pass