Fix update-assemblyinfo.ps1 for worktrees

BuildTools/update-assemblyinfo.ps1

@@ -38,22 +38,26 @@ function Find-Git() {
 	return $false;
 }
 
+function No-Git() {
+    return -not (((Test-Dir ".git") -or (Test-File ".git")) -and (Find-Git));
+}
+
 function gitVersion() {
-    if (-not ((Test-Dir ".git") -and (Find-Git))) {
+    if (No-Git) {
         return 0;
     }
     return [Int32]::Parse((git rev-list --count "$baseCommit..HEAD")) + $baseCommitRev;
 }
 
 function gitCommitHash() {
-    if (-not ((Test-Dir ".git") -and (Find-Git))) {
+    if (No-Git) {
         return "0000000000000000000000000000000000000000";
     }
     return (git rev-list "$baseCommit..HEAD") | Select -First 1;
 }
 
 function gitBranch() {
-    if (-not ((Test-Dir ".git" -or Test-File ".git") -and (Find-Git))) {
+    if (No-Git) {
         return "no-branch";
     }