Fabric: Improve docs; add example context managers

[klahnakoski]

The documentation shows how to execute a command with a particular code_dir

c.run("cd {} && git pull".format(code_dir))

Please change the example to use the cd() context manager. I have not idea how to do that.

http://www.fabfile.org/upgrading.html#actual-remote-steps

[mandarvaze]

The document referred above clearly says :

with cd is not fully implemented for the remote side of things

[pete312]

@mandarvaze cd is implemented with remote run. Some example in the documentation is what the OP is asking for. @klahnakoski this is how its done.

@task
def cd_example(ctx):
    ctx.run("pwd")
    with ctx.cd("/etc"):
        ctx.run("pwd")