project: fix m/ generation when switching manifest branches
project: fix m/ generation when switching manifest branches

We were updating the per-checkout m/ pseudo ref when syncing, but we
only created the common m/ redirect when initializing a project for
the first time.  This is fine unless the user switches the manifest
branch in an existing project, then we never create that redirect.

Bug: https://crbug.com/gerrit/14468
Change-Id: I5325e7e602dcb4ce150bef258901ba5e9fdea461
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/304822
Reviewed-by: Raman Tenneti <66788d848ab03efc83371cd4b586a3110f9172ef@google.com>
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@google.com>

lewixliu/git-repo,couchbasedeps/git-repo,couchbasedeps/git-repo,GerritCodeReview/git-repo,GerritCodeReview/git-repo,lewixliu/git-repo