Obtain --indent global flag value and pass it to store configs

[skirino]

To change number of spaces per indent level by command line flag. The current version (3.12.2) neglects --indent flag.
(Setting indent in .sops.yaml works as expected.)

To reproduce:

• Suppose I have an encrypted file (with age):

  $ age-keygen >key
  $ cat plain.json
  {
    "a": "b"
  }
  $ sops encrypt --age "$(age-keygen -y key)" plain.json --output enc.json
  

• Decrypting the file with and without --indent=2 gives the same output (indented with TABs in both cases):

  $ SOPS_AGE_KEY_FILE=key sops --indent=2 decrypt enc.json
  {
  	"a": "b"
  }
  $ SOPS_AGE_KEY_FILE=key sops decrypt enc.json
  {
  	"a": "b"
  }
  

[felixfontein]

Thanks for reporting and fixing this!