Support yml extension and remove mandatory file pattern

[d-rk]

Hi,

the restrictions on the secret names are very counter-intuitive. e.g.:

helm secrets dec secrets.yml
Decrypting secrets.yml
sops metadata not found
Error: plugin "secrets" exited with error

this fails, because yml is not supported. Additionally, the secret gets deleted with this :(

Currently the secret has to conform the following regex:
^secrets(.[^.]+)*.yaml$

This pull request removes the restriction completely and allows any *.yml / *.yaml to be processed.
Instead of relying on the filename the content of the file is checked to verify that it is a sops encrypted file.

Resolves #124, resolves #128

[Morriz]

any progress here?

[d-rk]

[Morriz]

I would suggest to cleanup the mixing of tabs and spaces, and only use two spaces (seeing that no specs are given in the repo).

[Morriz]

I can do a more thorough review later and see if I have rights to approve and if that is enough to merge ;p

[d-rk]

@Morriz the mixing of tabs and spaces was not introduced by this PR. This is also present on the master branch.
If this is fixed on master I can rebase the PR, but I don't think fixing this belongs into this PR.
Besides that, after roughly half a year has passed I'm not willing to but more time into this before knowing that this has a chance of being merged.