feat: support modification date reading from parent git repo (#661)

* feat: support modification date reading from parent git repo

* Print warning

* Fix formatting

* Update quartz/plugins/transformers/lastmod.ts

Co-authored-by: Jacky Zhao <j.zhao2k19@gmail.com>

---------

Co-authored-by: Jacky Zhao <j.zhao2k19@gmail.com>

quartz/plugins/transformers/lastmod.ts

@@ -57,10 +57,22 @@ export const CreatedModifiedDate: QuartzTransformerPlugin<Partial<Options> | und
                 published ||= file.data.frontmatter.publishDate
               } else if (source === "git") {
                 if (!repo) {
-                  repo = new Repository(file.cwd)
+                  // Get a reference to the main git repo.
+                  // It's either the same as the workdir,
+                  // or 1+ level higher in case of a submodule/subtree setup
+                  repo = Repository.discover(file.cwd)
                 }
 
-                modified ||= await repo.getFileLatestModifiedDateAsync(file.data.filePath!)
+                try {
+                  modified ||= await repo.getFileLatestModifiedDateAsync(file.data.filePath!)
+                } catch {
+                  console.log(
+                    chalk.yellow(
+                      `\nWarning: ${file.data
+                        .filePath!} isn't yet tracked by git, last modification date is not available for this file`,
+                    ),
+                  )
+                }
               }
             }