Added -input=false flag to init, plan, and apply steps

[austinorth]

fixes #268

Motivation

Atlantis needs to fail quickly and gracefully when user input is not provided for variables that are lacking a value.

What I Did

• Added the -input=false flag to init, plan and apply step runners. This flag is recommended by Hashicorp here.
• Added that same flag to the corresponding test files.

Difference in Output

Before Flag Added

exit status 1: running "sh -c terraform plan -refresh -no-color -out /home/<username>/.atlantis/repos/<repo> -var atlantis_user=austinorth" in "<directory>"
var.some_variable
  Enter a value: 
var.some_variable
  Enter a value: 
var.some_variable
  Enter a value: 
var.some_variable
  Enter a value: 

Error: Error asking for user input: missing required value for "some_variable"

After Flag Added

exit status 1: running "exit status 1: running "sh -c terraform plan -input=false -refresh -no-color -out /home/<username>/.atlantis/repos/<repo> -var atlantis_user=austinorth" in "<directory>"

Error: Required variable not set: some_variable

[lkysow]

Thanks looks good! I'll figure out the test problems.

[austinorth]

Thanks! I think I just figured it out. I didn't add the flag for the pre-Terraform 0.9 get command. Terraform doesn't have versioned docs, sadly, so I haven't yet been able to confirm if that flag exists in the earlier version.

[austinorth]

Update:
I downloaded Terraform 8.8 and looked at the help entry for the get command and found there are only two supported flags:

Options:

  -update=false       If true, modules already downloaded will be checked
                      for updates and updated if necessary.

  -no-color           If specified, output won't contain any color.

So I'll go ahead and roll back my change, but the test file will have to be modified to accommodate it. I'll leave that to you if that's ok!

[lkysow]

Yeah I'll do the tests

[lkysow]

Merged in #277 with fixed tests. Thanks so much Austin! I'll get this in the next release.