Change CLI messages to use CROC_SECRET

[01-1]

This pull request changes the cli messages to use CROC_SECRET.
Previously, the error message used export CROC_SECRET, which is unnecessary as you can just run CROC_SECRET=**** croc in one line.
Also, the messages for the sender used the classic command:

On the other computer run

croc ****

This made it incompatible with UNIX unless classic mode was activated.

The new command is

CROC_SECRET=**** croc

I also fixed a typo in the cli error messages.

[01-1]

Not sure if CROC_SECRET works on all platforms though (windows?)
If not, this should be edited to show commands for both UNIX and non-UNIX.

[schollz]

This isn't necessary on Windows. Can you change it to only print this on Unix systems (you can use runtime.GOOS == "windows")

[01-1]

The receiver system may not be the same as the sender. I changed this to print both commands.

[schollz]

CROC_SECRET is not needed on Windows, so please keep the regular print statements for Windows systems (if os.Runtime=="windows") and have your new print statement for non-windows

[schollz]

@01-1 does the suggested change make sense?

[01-1]

No, it doesn't - as per my comment, the receiver system may not be the same as the sender. For example, a windows system could send a file to a unix system, and vice versa.

[schollz]

I think its best to revert line 649 back to original. The receiver should interact with the messages

[01-1]

It doesn't make sense to tell the user to run a command that will not work by default.
Maybe just remove the command altogether

[schollz]

I think we can all agree that no one agrees on user interaction.

to me, the interaction makes sense because you type in croc PASSPHRASE and you get a explainer of all your options:

On UNIX systems, to receive with croc you either need
to set a code phrase using your environmental variables:

  export CROC_SECRET="****"
  croc

Or you can specify the code phrase when you run croc without
declaring the secret on the command line:

  croc
  Enter receive code: ****

Or you can go back to the classic croc behavior by enabling classic mode:

  croc --classic

versus having to have that information in the sender's purview also.

[01-1]

OK. It is much easier to be able to copy-paste the command though. Maybe add an option to print the unix command?

[schollz]

I mean, its pretty easy just to type croc on your receiver, press enter, and copy paste the password? if you are on a single computer, thats really the easiset

[nhtzr]

Hi. I arrived here because I wanted to propose a similar change. I believe a workflow that easily and quickly lets you do the right thing is valuable as it reduces the amount of frustation of anyone involved.

However I think the proposed message is hard to read, I would prefer something like:

Sending 'a.txt' (2.6 kB)         
Code is: 1106-yoyo-genius-patent

On the other computer run:
(For Windows)
    croc 1106-yoyo-genius-patent
(For Linux/OSX)
    CROC_SECRET="1106-yoyo-genius-patent" croc

Code would be

	fmt.Fprintf(os.Stderr, `Code is: %[1]s

On the other computer run:
(For Windows)
    croc %[2]s%[1]s
(For Linux/OSX)
    CROC_SECRET=%[1]q croc %[2]s
`, c.Options.SharedSecret, flags.String())

[schollz]

@nhtzr please submit a PR!