AC-branch usage suggestion

[Elan Ruusamäe]

...

because i hate duplication, here's some suggestion.

if you update spec that is not branch specific, commit it to HEAD, and move 
the AC-branch, rather commiting to AC-branch.

and if you still commit to branch, update HEAD too. don't rely somebody doing 
it for you. because if you don't and nobody will, eventually someday another 
developer updating the HEAD will lose the changes done in branch (or vice 
versa, but vice versa is probably not oblication to deviloper, but RM's 
worries)

there are plenty of cases where changes were overwritten, first two that come 
to my mind:
1. php-shared.patch with linking with current libphp_common.la
2. python patch which avoids linking with python-static

-- 
glen