fetchFromGitHub: use fetchgit when the rootDir option is set (#446709)

doc/build-helpers/fetchers.chapter.md

@@ -860,7 +860,14 @@ A number of fetcher functions wrap part of `fetchurl` and `fetchzip`. They are m
 
 To use a different GitHub instance, use `githubBase` (defaults to `"github.com"`).
 
-`fetchFromGitHub` uses `fetchzip` to download the source archive generated by GitHub for the specified revision. If `leaveDotGit`, `deepClone` or `fetchSubmodules` are set to `true`, `fetchFromGitHub` will use `fetchgit` instead. Refer to its section for documentation of these options.
+By default, `fetchFromGitHub` uses `fetchzip` to download GitHub's source archive for the specified revision.
+However, `fetchFromGitHub` will automatically switch to using `fetchgit` in any of these cases:
+
+- `forceFetchGit`, `leaveDotGit`, `deepClone`, `fetchLFS`, or `fetchSubmodules` are set to `true`
+- `sparseCheckout` contains any entries (is a non-empty list)
+- `rootDir` is set to a non-empty string
+
+When `fetchgit` is used, refer to the `fetchgit` section for documentation of its available options.
 
 ## `fetchFromGitLab` {#fetchfromgitlab}
 

pkgs/build-support/fetchgithub/default.nix

@@ -18,7 +18,8 @@ lib.makeOverridable (
     private ? false,
     forceFetchGit ? false,
     fetchLFS ? false,
-    sparseCheckout ? [ ],
+    rootDir ? "",
+    sparseCheckout ? lib.optional (rootDir != "") rootDir,
     githubBase ? "github.com",
     varPrefix ? null,
     meta ? { },
@@ -69,6 +70,7 @@ lib.makeOverridable (
       || deepClone
       || forceFetchGit
       || fetchLFS
+      || (rootDir != "")
       || (sparseCheckout != [ ]);
     # We prefer fetchzip in cases we don't need submodules as the hash
     # is more stable in that case.

pkgs/build-support/fetchgithub/tests.nix

@@ -0,0 +1,119 @@
+{ testers, fetchFromGitHub, ... }:
+{
+  simple = testers.invalidateFetcherByDrvHash fetchFromGitHub {
+    name = "simple-nix-source";
+    owner = "NixOS";
+    repo = "nix";
+    rev = "9d9dbe6ed05854e03811c361a3380e09183f4f4a";
+    hash = "sha256-7DszvbCNTjpzGRmpIVAWXk20P0/XTrWZ79KSOGLrUWY=";
+  };
+
+  sparseCheckout = testers.invalidateFetcherByDrvHash fetchFromGitHub {
+    name = "sparse-checkout-nix-source";
+    owner = "NixOS";
+    repo = "nix";
+    rev = "9d9dbe6ed05854e03811c361a3380e09183f4f4a";
+    sparseCheckout = [
+      "src"
+      "tests"
+    ];
+    sha256 = "sha256-g1PHGTWgAcd/+sXHo1o6AjVWCvC6HiocOfMbMh873LQ=";
+  };
+
+  sparseCheckoutNonConeMode = testers.invalidateFetcherByDrvHash fetchFromGitHub {
+    name = "sparse-checkout-non-cone-nix-source";
+    owner = "NixOS";
+    repo = "nix";
+    rev = "9d9dbe6ed05854e03811c361a3380e09183f4f4a";
+    sparseCheckout = [
+      "src"
+      "tests"
+    ];
+    nonConeMode = true;
+    sha256 = "sha256-FknO6C/PSnMPfhUqObD4vsW4PhkwdmPa9blNzcNvJQ4=";
+  };
+
+  leave-git = testers.invalidateFetcherByDrvHash fetchFromGitHub {
+    name = "leave-git-nix-source";
+    owner = "NixOS";
+    repo = "nix";
+    rev = "9d9dbe6ed05854e03811c361a3380e09183f4f4a";
+    sha256 = "sha256-VmQ38+lr+rNPaTnjjV41uC2XSN4fkfZAfytE2uKyLfo=";
+    leaveDotGit = true;
+  };
+
+  submodule-simple = testers.invalidateFetcherByDrvHash fetchFromGitHub {
+    name = "submodule-simple-source";
+    owner = "pineapplehunter";
+    repo = "nix-test-repo-with-submodule";
+    rev = "26473335b84ead88ee0a3b649b1c7fa4a91cfd4a";
+    sha256 = "sha256-rmP8PQT0wJBopdtr/hsB7Y/L1G+ZPdHC2r9LB05Qrj4=";
+    fetchSubmodules = true;
+  };
+
+  submodule-leave-git = testers.invalidateFetcherByDrvHash fetchFromGitHub {
+    name = "submodule-leave-git-source";
+    owner = "pineapplehunter";
+    repo = "nix-test-repo-with-submodule";
+    rev = "26473335b84ead88ee0a3b649b1c7fa4a91cfd4a";
+    sha256 = "sha256-EC2PMEEtA7f5OFdsluHn7pi4QXhCZuFML8tib4pV7Ek=";
+    leaveDotGit = true;
+    fetchSubmodules = true;
+  };
+
+  submodule-deep = testers.invalidateFetcherByDrvHash fetchFromGitHub {
+    name = "submodule-deep-source";
+    owner = "pineapplehunter";
+    repo = "nix-test-repo-with-submodule";
+    rev = "26473335b84ead88ee0a3b649b1c7fa4a91cfd4a";
+    sha256 = "sha256-3zWogs6EZBnzUfz6gBnigETTKGYl9KFKFgsy6Bl4DME=";
+    deepClone = true;
+    fetchSubmodules = true;
+    # deepClone implies leaveDotGit, so delete the .git directory after
+    # fetching to distinguish from the submodule-leave-git-deep test.
+    postFetch = "rm -r $out/.git";
+  };
+
+  submodule-leave-git-deep = testers.invalidateFetcherByDrvHash fetchFromGitHub {
+    name = "submodule-leave-git-deep-source";
+    owner = "pineapplehunter";
+    repo = "nix-test-repo-with-submodule";
+    rev = "26473335b84ead88ee0a3b649b1c7fa4a91cfd4a";
+    sha256 = "sha256-ieYn9I/0RgeSwQkSqwKaU3RgjKFlRqMg7zw0Nvu3azA=";
+    deepClone = true;
+    leaveDotGit = true;
+    fetchSubmodules = true;
+  };
+
+  dumb-http-signed-tag = testers.invalidateFetcherByDrvHash fetchFromGitHub {
+    name = "dumb-http-signed-tag-source";
+    owner = "NixOS";
+    repo = "nix";
+    tag = "2.9.2";
+    sha256 = "sha256-uZCaBo9rdWRO/AlQMvVVjpAwzYijB2H5KKQqde6eHkg=";
+  };
+
+  fetchTags = testers.invalidateFetcherByDrvHash fetchFromGitHub {
+    name = "fetchFromGitHub-fetch-tags-test";
+    owner = "NixOS";
+    repo = "nix";
+    rev = "9d9dbe6ed05854e03811c361a3380e09183f4f4a";
+    fetchTags = true;
+    leaveDotGit = true;
+    sha256 = "sha256-y7l+46lVP2pzJwGON5qEV0EoxWofRoWAym5q9VXvpc8=";
+    postFetch = ''
+      cd $out && git describe --tags --always > describe-output.txt 2>&1 || echo "git describe failed" > describe-output.txt
+      # See https://github.com/NixOS/nixpkgs/issues/412967#issuecomment-2927452118
+      rm -rf .git
+    '';
+  };
+
+  rootDir = testers.invalidateFetcherByDrvHash fetchFromGitHub {
+    name = "fetchFromGitHub-with-rootdir";
+    owner = "NixOS";
+    repo = "nix";
+    rev = "9d9dbe6ed05854e03811c361a3380e09183f4f4a";
+    rootDir = "misc/systemd";
+    hash = "sha256-UhxHk4SrXYq7ZDMtXLig5SigpbITrVgkpFTmryuvpcM=";
+  };
+}

pkgs/test/default.nix

@@ -140,6 +140,7 @@ with pkgs;
     callPackages ../build-support/fetchnextcloudapp/tests.nix { }
   );
   fetchFromBitbucket = recurseIntoAttrs (callPackages ../build-support/fetchbitbucket/tests.nix { });
+  fetchFromGitHub = recurseIntoAttrs (callPackages ../build-support/fetchgithub/tests.nix { });
   fetchFirefoxAddon = recurseIntoAttrs (
     callPackages ../build-support/fetchfirefoxaddon/tests.nix { }
   );