init: Add --use-local-gitdirs for standard Git layouts

Introduce --use-local-gitdirs to bypass repo's symlink-based layouts in
favor of standard local .git directories.

Bug: 513329573
Bug: 508146070
Change-Id: I53d1602e61be0b86964529bcbea3dc801471f9c9
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/569001
Tested-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Gavin Mak <gavinmak@google.com>
Reviewed-by: Dan Willemsen <dwillemsen@google.com>

man/repo-init.1

@@ -1,5 +1,5 @@
 .\" DO NOT MODIFY THIS FILE!  It was generated by help2man.
-.TH REPO "1" "September 2024" "repo init" "Repo Manual"
+.TH REPO "1" "April 2026" "repo init" "Repo Manual"
 .SH NAME
 repo \- repo init - manual page for repo init
 .SH SYNOPSIS
@@ -80,6 +80,10 @@ each project. See git archive.
 .TP
 \fB\-\-worktree\fR
 use git\-worktree to manage projects
+.TP
+\fB\-\-use\-local\-gitdirs\fR
+bypass .repo/projects/ and use standard Git layout in
+working tree
 .SS Project checkout optimizations:
 .TP
 \fB\-\-reference\fR=\fI\,DIR\/\fR