Ok, so I did some investigations and after a lot of trial and error, I finally came up with a solution. I will try to explain what I did, and why, for anyone who might need it.
From what I understood, implementation will add a depedency for both compiling and runtime (pretty sure it will only include API files for compiling if there are, but I'm not 100% sure), and will resolve any nested depedencies aswell, so its kinda neat if one's mod permenently depends on other's mod or API ! Though I need to control whether a mod is included during runtime or not, so I need to specify the scope of my depedencies.
I did some searches, and it turned out that Gradle will consume either jars or source folders regardless, so there is not a specific way to deal with one or the other it seems. I then tried the following and it worked like a charm (modified the commit branch / tags so its pointing to a permanent commit, more info here) !
depedencies {
compileOnly 'com.github.lazyMods:baubles:1.10.0.0-1.18:api'
runtimeOnly 'com.github.lazyMods:baubles:1.10.0.0-1.18'
}
But, whenever I try to run, the game crashes with a NoSuchMethod exception, pointing towards a method MenuScreens::m_96206_ called within the Baubles main class during ClientSetup (which is the unmapped name of MenuScreens::register) ; which is clearly a mapping issue. It confused me at first, but now that I think of it it's quite obvious : trying to run the game with uncompiled source files will cause all sorts of issues. And even if Jitpack seems to compile on the go those files, it will lack any metadata expected by Forge or ForgeGradle, so it's no use anyway.
The only two solutions I can think of are :
Download the mod jar, put it in a libs folder inside your workingDir that you can settup as a local repository, then add that jar as a runtime depedency
Use CurseMaven as a repository (as @diesieben07 suggested), and add the correct mod jar as a depedency (more info here)
I chose the latter, so now I have the following in my build.gradle file, and it works perfectly (one can even remove the ":api" from the baubles depedency to show the entire mod source files in Eclipse) :
repositories {
maven { url "https://cursemaven.com" content { includeGroup "curse.maven" } }
maven { url "https://jitpack.io" }
}
depedencies {
compileOnly "com.github.lazyMods:baubles:1.10.0.0-1.18:api"
runtimeOnly fg.deobf("curse.maven:baubles-366844:3576950") // Points toward Baubles: Reborn? v1.10.0.1-1.18.1 on curseforge.com
}
I couldn't use CurseMaven straight up as lazynessmind didn't provide a source jar or an api jar on curse forge just yet, so I had to use its Github instead to get the API, hence the struggle. I could have added the mod jar itself as an API, but then I would have to manualy add the source files for Eclipse, which then makes this whole "manage your depedencies solely with Gradle" obsolete...
Thanks for the help, as I could not figure out those things on my own ! I hope that may be usefull to someone some day !