sbt: allow managing the ~/.sbt/repositories file

sbt allows overriding the default repositories to use to resolve
dependencies. This is often used with proxies and/or private
repositories to host internal packages.

This change adds a `repositories` attribute to `sbt` to allow
specifying the values that will go in `~/.sbt/repositories` file.

To support the above change we also deprecate the `baseConfigPath`
option in favour of `baseUserConfigPath` which points one level higher
by default. This allows not using relative paths to refer to the
top-level configuration directory.

Also adds tests for the new option and the deprecation of the previous
one.

modules/programs/sbt.nix

@@ -16,6 +16,17 @@ let
     import scala.sys.process._
     ${concatStrings (map renderCredential creds)}'';
 
+  renderRepository = value:
+    if isString value then ''
+      ${value}
+    '' else ''
+      ${concatStrings (mapAttrsToList (name: value: "${name}: ${value}") value)}
+    '';
+
+  renderRepositories = repos: ''
+    [repositories]
+    ${concatStrings (map renderRepository cfg.repositories)}'';
+
   sbtTypes = {
     plugin = types.submodule {
       options = {
@@ -68,6 +79,11 @@ let
   cfg = config.programs.sbt;
 
 in {
+  imports = [
+    (mkRemovedOptionModule [ "programs" "sbt" "baseConfigPath" ]
+      "Use programs.sbt.baseUserConfigPath instead, but note that the semantics are slightly different.")
+  ];
+
   meta.maintainers = [ maintainers.kubukoz ];
 
   options.programs.sbt = {
@@ -80,10 +96,13 @@ in {
       description = "The package with sbt to be installed.";
     };
 
-    baseConfigPath = mkOption {
+    baseUserConfigPath = mkOption {
       type = types.str;
-      default = ".sbt/1.0";
-      description = "Where the plugins and credentials should be located.";
+      default = ".sbt";
+      description = ''
+        Where the sbt configuration files should be located, relative
+        <envar>HOME</envar>.
+      '';
     };
 
     plugins = mkOption {
@@ -123,19 +142,63 @@ in {
         A list of credentials to define in the sbt configuration directory.
       '';
     };
+
+    repositories = mkOption {
+      type = with types;
+        listOf
+        (either (enum [ "local" "maven-central" "maven-local" ]) (attrsOf str));
+      default = [ ];
+      example = literalExpression ''
+        [
+          "local"
+          { my-ivy-proxy-releases = "http://repo.company.com/ivy-releases/, [organization]/[module]/(scala_[scalaVersion]/)(sbt_[sbtVersion]/)[revision]/[type]s/[artifact](-[classifier]).[ext]" }
+          { my-maven-proxy-releases = "http://repo.company.com/maven-releases/" }
+          "maven-central"
+        ]
+      '';
+      description = ''
+        A list of repositories to use when resolving dependencies. Defined as a
+        list of pre-defined repository or custom repository as a set of name to
+        URL. The list will be used populate the <code>~/.sbt/repositories</code>
+        file in the order specified.
+
+        </para><para>
+
+        Pre-defined repositories must be one of <code>local</code>,
+        <code>maven-local</code>, <code>maven-central</code>.
+
+        </para><para>
+
+        Custom repositories are defined as
+        <code language="nix">{ name-of-repo = "https://url.to.repo.com"}</code>.
+
+        </para><para>
+
+        See
+        <link xlink:href="https://www.scala-sbt.org/1.x/docs/Launcher-Configuration.html#3.+Repositories+Section"/>
+        about this configuration section and
+        <link xlink:href="https://www.scala-sbt.org/1.x/docs/Proxy-Repositories.html"/>
+        to read about proxy repositories.
+      '';
+    };
   };
 
   config = mkIf cfg.enable (mkMerge [
     { home.packages = [ cfg.package ]; }
 
     (mkIf (cfg.plugins != [ ]) {
-      home.file."${cfg.baseConfigPath}/plugins/plugins.sbt".text =
+      home.file."${cfg.baseUserConfigPath}/1.0/plugins/plugins.sbt".text =
         concatStrings (map renderPlugin cfg.plugins);
     })
 
     (mkIf (cfg.credentials != [ ]) {
-      home.file."${cfg.baseConfigPath}/credentials.sbt".text =
+      home.file."${cfg.baseUserConfigPath}/1.0/credentials.sbt".text =
         renderCredentials cfg.credentials;
     })
+
+    (mkIf (cfg.repositories != [ ]) {
+      home.file."${cfg.baseUserConfigPath}/repositories".text =
+        renderRepositories cfg.repositories;
+    })
   ]);
 }