stdenv: re-add meta.repository

doc/stdenv/meta.chapter.md

@@ -47,6 +47,10 @@ Release branch. Used to specify that a package is not going to receive updates t
 
 The package’s homepage. Example: `https://www.gnu.org/software/hello/manual/`
 
+### `repository` {#var-meta-repository}
+
+A webpage (or list of webpages) where the package's source code can be viewed.  `https` links are preferred if available.  Automatically set to a default value if the package uses a `fetchFrom*` fetcher for its `src`. Example: `https://gitlab.freedesktop.org/libfprint/fprintd/`
+
 ### `downloadPage` {#var-meta-downloadPage}
 
 The page where a link to the current version can be found. Example: `https://ftp.gnu.org/gnu/hello/`

pkgs/stdenv/generic/check-meta.nix

@@ -11,6 +11,8 @@ let
     concatMapStringsSep
     concatStrings
     findFirst
+    filter
+    head
     isDerivation
     length
     concatMap
@@ -303,6 +305,10 @@ let
       (listOf str)
       str
     ];
+    repository = union [
+      (listOf str)
+      str
+    ];
     downloadPage = str;
     changelog = union [
       (listOf str)
@@ -440,6 +446,10 @@ let
     # -----
     else { valid = "yes"; });
 
+  unlist = list:
+    if length list == 1
+    then head list
+    else list;
 
   # The meta attribute is passed in the resulting attribute set,
   # but it's not part of the actual derivation, i.e., it's not
@@ -454,6 +464,15 @@ let
       hasOutput = out: builtins.elem out outputs;
     in
     {
+      # get the default value for the meta.repository field.
+      # the fetchFrom* fetchers set src.meta.homepage
+      # NOTE: this will fail if src fails to eval, in that case either set meta.repository manually to prevent this default from being evaluated, or just make sure src doesn't fail to eval.
+      repository =
+        if attrs ? src.meta.homepage
+        then attrs.src.meta.homepage
+        else if attrs ? srcs && isList attrs.srcs
+        then unlist (map (src: src.meta.homepage) (filter (src: src ? meta.homepage) attrs.srcs))
+        else [];
       # `name` derivation attribute includes cross-compilation cruft,
       # is under assert, and is sanitized.
       # Let's have a clean always accessible version here.