Git fetcher: Restore progress indication

We were calling git with `--quiet` in order not to mess up Nix's
progress bar. However, `runProgram()` already suspends the progress
bar (since git may be interactive) so that's no longer an issue. So we
can just run with `--progress` instead.

Author: edolstra

src/libfetchers/git-utils.cc

@@ -582,25 +582,15 @@ struct GitRepoImpl : GitRepo, std::enable_shared_from_this<GitRepoImpl>
         //       then use code that was removed in this commit (see blame)
 
         auto dir = this->path;
-        Strings gitArgs{"-C", dir.string(), "--git-dir", ".", "fetch", "--quiet", "--force"};
+        Strings gitArgs{"-C", dir.string(), "--git-dir", ".", "fetch", "--progress", "--force"};
         if (shallow)
             append(gitArgs, {"--depth", "1"});
         append(gitArgs, {std::string("--"), url, refspec});
 
-        auto [status, output] = runProgram(
-            RunOptions{
-                .program = "git",
-                .lookupPath = true,
-                // FIXME: git stderr messes up our progress indicator, so
-                // we're using --quiet for now. Should process its stderr.
-                .args = gitArgs,
-                .input = {},
-                .mergeStderrToStdout = true,
-                .isInteractive = true});
+        auto status = runProgram(RunOptions{.program = "git", .args = gitArgs, .isInteractive = true}).first;
 
-        if (status > 0) {
-            throw Error("Failed to fetch git repository %s : %s", url, output);
-        }
+        if (status > 0)
+            throw Error("Failed to fetch git repository '%s'", url);
     }
 
     void verifyCommit(const Hash & rev, const std::vector<fetchers::PublicKey> & publicKeys) override