Git - fix edge case with Windows mapped drives (microsoft#154342)

* Fix an edge case with computing relative path on Windows

* Refactor the fix

Author: lszomoru

extensions/git/src/git.ts

@@ -475,8 +475,9 @@ export class Git {
 		const repoPath = path.normalize(result.stdout.trimLeft().replace(/[\r\n]+$/, ''));
 
 		if (isWindows) {
-			// On Git 2.25+ if you call `rev-parse --show-toplevel` on a mapped drive, instead of getting the mapped drive path back, you get the UNC path for the mapped drive.
-			// So we will try to normalize it back to the mapped drive path, if possible
+			// On Git 2.25+ if you call `rev-parse --show-toplevel` on a mapped drive, instead of getting the mapped
+			// drive path back, you get the UNC path for the mapped drive. So we will try to normalize it back to the
+			// mapped drive path, if possible
 			const repoUri = Uri.file(repoPath);
 			const pathUri = Uri.file(repositoryPath);
 			if (repoUri.authority.length !== 0 && pathUri.authority.length === 0) {
@@ -504,6 +505,13 @@ export class Git {
 
 				return path.normalize(pathUri.fsPath);
 			}
+
+			// On Windows, there are cases in which the normalized path for a mapped folder contains a trailing `\`
+			// character (ex: \\server\folder\) due to the implementation of `path.normalize()`. This behaviour is
+			// by design as documented in https://github.com/nodejs/node/issues/1765.
+			if (repoUri.authority.length !== 0) {
+				return repoPath.replace(/\\$/, '');
+			}
 		}
 
 		return repoPath;