fetchFromGitHub: fix fetchSubmodules=true when revision is not hexadecimal

pkgs/build-support/fetchgit/default.nix

@@ -1,21 +1,9 @@
-{stdenv, git, cacert}: let
-  urlToName = url: rev: let
-    inherit (stdenv.lib) removeSuffix splitString last;
-    base = last (splitString ":" (baseNameOf (removeSuffix "/" url)));
+{stdenv, git, cacert, gitRepoToName}:
 
-    matched = builtins.match "(.*).git" base;
-
-    short = builtins.substring 0 7 rev;
-
-    appendShort = if (builtins.match "[a-f0-9]*" rev) != null
-      then "-${short}"
-      else "";
-  in "${if matched == null then base else builtins.head matched}${appendShort}";
-in
 { url, rev ? "HEAD", md5 ? "", sha256 ? "", leaveDotGit ? deepClone
 , fetchSubmodules ? true, deepClone ? false
 , branchName ? null
-, name ? urlToName url rev
+, name ? gitRepoToName url rev
 , # Shell code executed after the file has been fetched
   # successfully. This can do things like check or transform the file.
   postFetch ? ""

pkgs/build-support/fetchgit/gitrepotoname.nix

@@ -0,0 +1,14 @@
+{ lib }:
+
+urlOrRepo: rev: let
+  inherit (lib) removeSuffix splitString last;
+  base = last (splitString ":" (baseNameOf (removeSuffix "/" urlOrRepo)));
+
+  matched = builtins.match "(.*).git" base;
+
+  short = builtins.substring 0 7 rev;
+
+  appendShort = if (builtins.match "[a-f0-9]*" rev) != null
+    then "-${short}"
+    else "";
+in "${if matched == null then base else builtins.head matched}${appendShort}"

pkgs/build-support/fetchgit/nix-prefetch-git

@@ -282,8 +282,8 @@ _clone_user_rev() {
             if test -z "$(echo "$rev" | tr -d 0123456789abcdef)"; then
                 clone "$dir" "$url" "$rev" "" 1>&2
             else
-                echo 1>&2 "Bad commit hash or bad reference."
-                exit 1
+                # if revision is not hexadecimal it might be a tag
+                clone "$dir" "$url" "" "refs/tags/$rev" 1>&2
             fi;;
     esac