libutil: Expose spawnProgram and implement fd redirections

src/libcmd/repl.cc

@@ -510,9 +510,12 @@ ProcessLineResult NixRepl::processLine(std::string line)
         // runProgram redirects stdout to a StringSink,
         // using runProgram2 to allow editors to display their UI
         runProgram2({
-            .program = editor,
-            .lookupPath = true,
-            .args = std::move(args),
+            .spawnOptions =
+                {
+                    .program = editor,
+                    .lookupPath = true,
+                    .args = std::move(args),
+                },
             .isInteractive = true,
         });
 

src/libfetchers/git-lfs-fetch.cc

@@ -73,7 +73,7 @@ LfsApiInfo getLfsApi(ParsedURL url)
         args.push_back(string_to_os_string(url.renderPath(/*encode=*/false)));
         args.push_back(OS_STR("download"));
 
-        auto [status, output] = runProgram({.program = "ssh", .args = args});
+        auto [status, output] = runProgram({{.program = "ssh", .args = args}});
 
         if (output.empty())
             throw Error(

src/libfetchers/git-utils.cc

@@ -750,7 +750,14 @@ struct GitRepoImpl : GitRepo, std::enable_shared_from_this<GitRepoImpl>
         gitArgs.push_back(string_to_os_string(url));
         gitArgs.push_back(string_to_os_string(refspec));
 
-        auto status = runProgram({.program = GIT_PROGRAM, .args = gitArgs, .isInteractive = true}).first;
+        auto [status, _] = runProgram({
+            .spawnOptions =
+                {
+                    .program = GIT_PROGRAM,
+                    .args = gitArgs,
+                },
+            .isInteractive = true,
+        });
 
         if (status > 0)
             throw Error("Failed to fetch git repository '%s'", url);
@@ -791,15 +798,18 @@ struct GitRepoImpl : GitRepo, std::enable_shared_from_this<GitRepoImpl>
 
         // Run verification command
         auto [status, output] = runProgram({
-            .program = GIT_PROGRAM,
-            .args{
-                OS_STR("-c"),
-                OS_STR("gpg.ssh.allowedSignersFile=") + allowedSignersFile.native(),
-                OS_STR("-C"),
-                path.native(),
-                OS_STR("verify-commit"),
-                string_to_os_string(rev.gitRev()),
-            },
+            .spawnOptions =
+                {
+                    .program = GIT_PROGRAM,
+                    .args{
+                        OS_STR("-c"),
+                        OS_STR("gpg.ssh.allowedSignersFile=") + allowedSignersFile.native(),
+                        OS_STR("-C"),
+                        path.native(),
+                        OS_STR("verify-commit"),
+                        string_to_os_string(rev.gitRev()),
+                    },
+                },
             .mergeStderrToStdout = true,
         });
 

src/libfetchers/git.cc

@@ -51,9 +51,12 @@ std::optional<std::string> readHead(const std::filesystem::path & path)
 {
     auto [status, output] = runProgram(
         RunOptions{
-            .program = GIT_PROGRAM,
-            // FIXME: use 'HEAD' to avoid returning all refs
-            .args = {OS_STR("ls-remote"), OS_STR("--symref"), path.native()},
+            .spawnOptions =
+                {
+                    .program = GIT_PROGRAM,
+                    // FIXME: use 'HEAD' to avoid returning all refs
+                    .args = {OS_STR("ls-remote"), OS_STR("--symref"), path.native()},
+                },
             .isInteractive = true,
         });
     if (status != 0)
@@ -501,16 +504,16 @@ struct GitInputScheme : InputScheme
 
         auto result = runProgram(
             RunOptions{
-                .program = GIT_PROGRAM,
-                .args{
-                    OS_STR("-C"),
-                    repoPath->native(),
-                    OS_STR("--git-dir"),
-                    string_to_os_string(repoInfo.gitDir),
-                    OS_STR("check-ignore"),
-                    OS_STR("--quiet"),
-                    string_to_os_string(std::string(path.rel())),
-                },
+                {.program = GIT_PROGRAM,
+                 .args{
+                     OS_STR("-C"),
+                     repoPath->native(),
+                     OS_STR("--git-dir"),
+                     string_to_os_string(repoInfo.gitDir),
+                     OS_STR("check-ignore"),
+                     OS_STR("--quiet"),
+                     string_to_os_string(std::string(path.rel())),
+                 }},
             });
         auto exitCode =
 #ifndef WIN32 // TODO abstract over exit status handling on Windows

src/libfetchers/mercurial.cc

@@ -24,7 +24,12 @@ static RunOptions hgOptions(OsStrings args)
     // Set HGPLAIN: this means we get consistent output from hg and avoids leakage from a user or system .hgrc.
     env[OS_STR("HGPLAIN")] = OS_STR("");
 
-    return {.program = HG_PROGRAM, .lookupPath = true, .args = std::move(args), .environment = env};
+    return {{
+        .program = HG_PROGRAM,
+        .lookupPath = true,
+        .args = std::move(args),
+        .environment = env,
+    }};
 }
 
 // runProgram wrapper that uses hgOptions instead of stock RunOptions.

src/libmain/shared.cc

@@ -381,7 +381,7 @@ RunPager::RunPager()
         return;
 
 /* TODO re-enable on Windows, once a child can be given our pipe as its
-   stdin: `RunOptions` has no `standardIn`, and `spawnProcess` hardcodes a
+   stdin: `RunOptions` has no `standardIn`, and `spawnProgram` hardcodes a
    null one. Printing unpaged beats failing the command. */
 #ifdef _WIN32
     return;

src/libstore/build/derivation-builder-impl.cc

@@ -45,14 +45,16 @@ static void handleDiffHook(
     try {
         auto diffRes = runProgram(
             RunOptions{
-                .program = diffHook,
-                .lookupPath = true,
-                .args = {tryA, tryB, drvPath, tmpDir},
+                .spawnOptions =
+                    {.program = diffHook,
+                     .lookupPath = true,
+                     .args = {tryA, tryB, drvPath, tmpDir},
 #ifndef _WIN32
-                .uid = uid,
-                .gid = gid,
+                     .uid = uid,
+                     .gid = gid,
 #endif
-                .chdir = "/"});
+                     .chdir = "/"},
+            });
         if (!statusOk(diffRes.first))
             throw ExecError(diffRes.first, "diff-hook program %s %s", PathFmt(diffHook), statusToString(diffRes.first));
 

src/libstore/build/derivation-building-goal.cc

@@ -1085,8 +1085,8 @@ Goal::Co DerivationBuildingGoal::buildLocally(
         if (worker.settings.postBuildHook.get() != "") {
 #ifdef _WIN32
             /* Nothing here needs `fork`: the child only sets the environment,
-               redirects stdout/stderr and execs, which `spawnProcess` already
-               does. What is missing is that `spawnProcess` is not exported,
+               redirects stdout/stderr and execs, which `spawnProgram` already
+               does. What is missing is that `spawnProgram` is not exported,
                and that the worker needs an `AsyncPipe` tied to the completion
                port rather than the plain `Pipe` this produces. Throw rather
                than silently skip the hook. */

src/libstore/include/nix/store/ssh.hh

@@ -40,9 +40,7 @@ private:
     void addCommonSSHOpts(OsStrings & args);
     bool isMasterRunning();
 
-#ifndef _WIN32 // TODO re-enable on Windows, once we can fork.
     std::filesystem::path startMaster();
-#endif
 
 public: