Fail On Duplicate Config Names

[paulgibert]

Fixes #1599

• Updated wolfictl lint to fail if a duplicate package config name is encountered.
• Added a unit test to melange_test.go for duplicate package config names

Steps to test:

1. See that lint succeeds on a valid repo:

git clone https://github.com/wolfi-dev/os.git
cd os
wolfictl lint -s error

# Should succeed

2. See that introducing duplicate configs results in an error:

# From inside os/

echo "package:\n  name: duplicate\n  version: 1.2.3" > duplicate1.yaml
cp duplicate1.yaml duplicate2.yaml
wolfictl lint -s error

# Example output: 2024/12/13 11:44:33 ERRO Package config names must be unique. Found duplicate 'duplicate'

The check happens in pkg/melange as this is where the duplicates were ignored as pointed out in #1599. An alternative but more complex solution would be to add a new lint rule. I didn't go that route because it would require a notable ABI change.

#first-golang-pr (let's go)

@priyawadhwa

[imjasonh]

I think we might also want to fail if .package.name is not the same as the filename.

These are potentially different/separate issues, but it does I think violate some assumptions we've made, and is worth avoiding.

If we have that check, we also get uniqueness "for free" since there can't be two foo.yamls

[paulgibert]

If the .package.name field must match the filename, couldn't you make an argument that the field is redundant and should be removed?

[priyawadhwa]

It might be helpful to include the file names for the duplicate packages in the error message so it's easier to fix