Fix the printed path of the ".repo" dir after a fresh init.
Fix the printed path of the ".repo" dir after a fresh init.

Apparently, manifest.topdir already contains a trailing slash in some
cases, so a simple string concatenation may or not lead to double
slashes. It is safer to use os.path.join. See
https://screenshot.googleplex.com/6pSY3QewAeCdAqk

Change-Id: I2411452296b7e78fc975787b675273a48d6b3d85
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/341574
Reviewed-by: LaMont Jones <01939f9990a33aa2509cfaed21d2f9ba201a2b37@google.com>
Tested-by: Mateus Azis <6163e6a9c5c30ef7ad487969e88c1ed390562f2f@google.com>

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