SSH config 'user' value is ignored in execute()

[stefanha]

The following lines in network.py:normalize() cause the SSH config 'user' value to be ignored when the task is invoked via execute():

# Only use ssh_config values if the env value appears unmodified from
# the true defaults. If the user has tweaked them, that new value
# takes precedence.
if user == env.local_user and 'user' in conf:
    user = conf['user']

The parent task may have a user value that differs from env.local_user so the if condition is False.

The following fabfile reproduces the bug:

from fabric.api import *

@hosts('host2')
def a():
    print env.user

def b():
    execute('a')

# When .ssh/config has:
# Host host1
# User user1
# Host host2
# User user2
#
# Output:
# $ fab -H host1 a
# user2
# $ fab -H host1 b
# user1
#
# A different user value is set depending on whether task 'a' was invoked from
# the command-line or via execute()!
#
# The expected output is:
# $ fab -H host1 b
# user2

[stefanha]

After discussing with redkrieg on IRC I think comparing against a user value in network.py:normalize() is wrong in the first place. If the user manually overrides env.user but happens to use same username as env.local_user they're not supposed to get the ssh config User value, but the current code will treat it as if it's okay to apply ssh config User.