commands: document the "common" class attribute

Switch it to uppercase to make it clear it's a constant, and add
documentation so its usage is clear.

Change-Id: I6d281a66a90b5908b3131585c9945e88cfe815ea
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/309322
Reviewed-by: Raman Tenneti <rtenneti@google.com>
Tested-by: Mike Frysinger <vapier@google.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/subcmds/selfupdate.py b/subcmds/selfupdate.py
index 388881d9..282f518e 100644
--- a/subcmds/selfupdate.py
+++ b/subcmds/selfupdate.py
@@ -21,7 +21,7 @@ from subcmds.sync import _PostRepoFetch
 
 
 class Selfupdate(Command, MirrorSafeCommand):
-  common = False
+  COMMON = False
   helpSummary = "Update repo to the latest version"
   helpUsage = """
 %prog