fix(mcl.utils.path.rootDir): Handle the case where we're not in a git repo

Which is the case when `actions/checkout` has not been ran.

Author: PetarKirov

packages/mcl/src/src/mcl/commands/ci_matrix.d

@@ -422,7 +422,7 @@ unittest
 
 void saveGHCIComment(SummaryTableEntry[] tableSummaryJSON)
 {
-    import std.path : buildPath, absolutePath;
+    import std.path : buildNormalizedPath, absolutePath;
 
     string comment = "Thanks for your Pull Request!";
     comment ~= "\n\nBelow you will find a summary of the cachix status of each package, for each supported platform.";
@@ -432,7 +432,7 @@ void saveGHCIComment(SummaryTableEntry[] tableSummaryJSON)
         pkg => "\n| " ~ pkg.name ~ " | " ~ pkg.x86_64.linux ~ " | " ~ pkg.x86_64.darwin ~ " | " ~ pkg.aarch64.darwin ~ " |")
         .join("");
 
-    auto outputPath = rootDir.buildPath("comment.md").absolutePath;
+    auto outputPath = rootDir.buildNormalizedPath("comment.md");
     write(outputPath, comment);
     infof("Wrote GitHub comment file to '%s'", outputPath);
 }

packages/mcl/src/src/mcl/utils/path.d

@@ -1,18 +1,17 @@
 module mcl.utils.path;
-import mcl.utils.test;
 
 import std.process : execute;
 import std.string : strip;
 import std.file : mkdirRecurse, rmdir, exists;
-import std.path : buildPath;
+import std.path : buildNormalizedPath, absolutePath;
 
 immutable string rootDir, resultDir, gcRootsDir;
 
 shared static this()
 {
     rootDir = getTopLevel();
-    resultDir = rootDir.buildPath(".result");
-    gcRootsDir = resultDir.buildPath("gc-roots");
+    resultDir = rootDir.buildNormalizedPath(".result");
+    gcRootsDir = resultDir.buildNormalizedPath("gc-roots");
 }
 
 string getTopLevel()
@@ -23,7 +22,11 @@ string getTopLevel()
     if (isNixbld)
         return environment["NIX_BUILD_TOP"];
 
-    return execute(["git", "rev-parse", "--show-toplevel"]).output.strip;
+    auto res = execute(["git", "rev-parse", "--show-toplevel"]);
+    if (res.status != 0)
+        return ".".absolutePath.buildNormalizedPath;
+
+    return res.output.strip;
 }
 
 @("rootDir")
@@ -35,13 +38,13 @@ unittest
 @("resultDir")
 unittest
 {
-    assert(resultDir == rootDir.buildPath(".result"));
+    assert(resultDir == rootDir.buildNormalizedPath(".result"));
 }
 
 @("gcRootsDir")
 unittest
 {
-    assert(gcRootsDir == resultDir.buildPath("gc-roots"));
+    assert(gcRootsDir == resultDir.buildNormalizedPath("gc-roots"));
 }
 
 void createResultDirs()