fix: allow tilde character when specifying a local repository (#316)

There already exists a function that will convert a tilde path to an absolute path. It was originally used for this purpose, but the functionality was removed during a commit that changed which function was used to validate git repositories.

This reinstates that functionality and allows us to type a ~/ tilde path to get our home directories when typing in a path.

app/src/ui/add-repository/add-existing-repository.tsx

@@ -16,6 +16,7 @@ import { showOpenDialog } from '../main-process-proxy'
 import { Ref } from '../lib/ref'
 import { InputError } from '../lib/input-description/input-error'
 import { IAccessibleMessage } from '../../models/accessible-message'
+import { isGitRepository } from './create-repository'
 
 interface IAddExistingRepositoryProps {
   readonly dispatcher: Dispatcher
@@ -278,9 +279,9 @@ export class AddExistingRepository extends React.Component<
   }
 
   private onPathChanged = async (path: string) => {
-    if (this.state.path !== path) {
-      this.updatePath(path)
-    }
+    const isRepository = await isGitRepository(this.resolvedPath(path))
+
+    this.setState({ path, isRepository })
   }
 
   private showFilePicker = async () => {