Add $auto_subscribe variable.

When set, it automatically subscribes to mailing lists found in
List-Post headers.

This commit is based on Michael Elkins's patch from the thread
<https://marc.info/?l=mutt-users&m=127076105423565&w=2>.

I've added an opt-in variable $auto_subscribe and a hash table cache
to speed up reading headers when the variable is set.

1 files changed, 1 insertions, 0 deletions

diff --git a/globals.h b/globals.h
index cecb46d6..d71fc779 100644
--- a/globals.h
+++ b/globals.h
@@ -170,6 +170,7 @@ WHERE const char *ReleaseDate;
 
 WHERE HASH *Groups;
 WHERE HASH *ReverseAlias;
+WHERE HASH *AutoSubscribeCache;
 
 WHERE LIST *AutoViewList INITVAL(0);
 WHERE LIST *AlternativeOrderList INITVAL(0);