fetchFromSourcehut: add tag as an alternative for rev

This is just for consistency with fetchFromGitHub and fetchFromGitLab
since the URLs used are the same.

Signed-off-by: Marcin Serwin <marcin@serwin.dev>

pkgs/build-support/fetchsourcehut/default.nix

@@ -18,14 +18,21 @@ makeOverridable (
   {
     owner,
     repo,
-    rev,
-    name ? repoRevToNameMaybe repo rev "sourcehut",
+    rev ? null,
+    tag ? null,
+    name ? repoRevToNameMaybe repo (lib.revOrTag rev tag) "sourcehut",
     domain ? "sr.ht",
     vc ? "git",
     fetchSubmodules ? false,
     ... # For hash agility
   }@args:
 
+  assert (
+    lib.assertMsg (lib.xor (tag == null) (
+      rev == null
+    )) "fetchFromSourcehut requires one of either `rev` or `tag` to be provided (not both)."
+  );
+
   assert (
     assertOneOf "vc" vc [
       "hg"
@@ -35,6 +42,7 @@ makeOverridable (
 
   let
     urlFor = resource: "https://${resource}.${domain}/${owner}/${repo}";
+    rev' = if tag != null then tag else rev;
     baseUrl = urlFor vc;
     baseArgs = {
       inherit name;
@@ -43,13 +51,14 @@ makeOverridable (
       "owner"
       "repo"
       "rev"
+      "tag"
       "domain"
       "vc"
       "name"
       "fetchSubmodules"
     ];
     vcArgs = baseArgs // {
-      inherit rev;
+      rev = rev';
       url = baseUrl;
     };
     fetcher = if fetchSubmodules then vc else "zip";
@@ -69,7 +78,7 @@ makeOverridable (
       zip = {
         fetch = fetchzip;
         arguments = baseArgs // {
-          url = "${baseUrl}/archive/${rev}.tar.gz";
+          url = "${baseUrl}/archive/${rev'}.tar.gz";
           postFetch = optionalString (vc == "hg") ''
             rm -f "$out/.hg_archival.txt"
           ''; # impure file; see #12002
@@ -82,7 +91,7 @@ makeOverridable (
   in
   cases.${fetcher}.fetch cases.${fetcher}.arguments
   // {
-    inherit rev;
+    rev = rev';
     meta.homepage = "${baseUrl}";
   }
 )