Merge branch 'master' into staging

... to get the systemd update (rebuilding ~7k jobs).

lib/lists.nix

@@ -24,7 +24,7 @@ rec {
      Example:
        concat = fold (a: b: a + b) "z"
        concat [ "a" "b" "c" ]
-       => "abcnul"
+       => "abcz"
   */
   fold = op: nul: list:
     let

lib/sources.nix

@@ -29,4 +29,30 @@ rec {
       in type == "directory" || lib.any (ext: lib.hasSuffix ext base) exts;
     in builtins.filterSource filter path;
 
+  # Get the commit id of a git repo
+  # Example: commitIdFromGitRepo <nixpkgs/.git>
+  commitIdFromGitRepo =
+    let readCommitFromFile = path: file:
+      with builtins;
+        let fileName       = toString path + "/" + file;
+            packedRefsName = toString path + "/packed-refs";
+        in if lib.pathExists fileName
+           then
+             let fileContent = readFile fileName;
+                 # Sometimes git stores the commitId directly in the file but
+                 # sometimes it stores something like: «ref: refs/heads/branch-name»
+                 matchRef    = match "^ref: (.*)\n$" fileContent;
+             in if   isNull matchRef
+                then lib.removeSuffix "\n" fileContent
+                else readCommitFromFile path (lib.head matchRef)
+           # Sometimes, the file isn't there at all and has been packed away in the
+           # packed-refs file, so we have to grep through it:
+           else if lib.pathExists packedRefsName
+           then
+             let packedRefs  = lib.splitString "\n" (readFile packedRefsName);
+                 matchRule   = match ("^(.*) " + file + "$");
+                 matchedRefs = lib.flatten (lib.filter (m: ! (isNull m)) (map matchRule packedRefs));
+             in lib.head matchedRefs
+           else throw ("Not a .git directory: " + path);
+    in lib.flip readCommitFromFile "HEAD";
 }

lib/types.nix

@@ -114,13 +114,17 @@ rec {
       name = "list of ${elemType.name}s";
       check = isList;
       merge = loc: defs:
-        map (x: x.value) (filter (x: x ? value) (concatLists (imap (n: def: imap (m: def':
-            (mergeDefinitions
-              (loc ++ ["[definition ${toString n}-entry ${toString m}]"])
-              elemType
-              [{ inherit (def) file; value = def'; }]
-            ).optionalValue
-          ) def.value) defs)));
+        map (x: x.value) (filter (x: x ? value) (concatLists (imap (n: def:
+          if isList def.value then
+            imap (m: def':
+              (mergeDefinitions
+                (loc ++ ["[definition ${toString n}-entry ${toString m}]"])
+                elemType
+                [{ inherit (def) file; value = def'; }]
+              ).optionalValue
+            ) def.value
+          else
+            throw "The option value `${showOption loc}' in `${def.file}' is not a list.") defs)));
       getSubOptions = prefix: elemType.getSubOptions (prefix ++ ["*"]);
       getSubModules = elemType.getSubModules;
       substSubModules = m: listOf (elemType.substSubModules m);