docs: smart-sync: split out & expand details

The existing documentation on smart-sync behavior is a bit light on
details, and out of date wrt what the code actually does.  Start a
dedicated document and fill it out more.

Change-Id: I1a8a3ac6edf9291d72182ad55db865035d9b683e
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/450002
Commit-Queue: Mike Frysinger <vapier@google.com>
Tested-by: Mike Frysinger <vapier@google.com>
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/subcmds/sync.py b/subcmds/sync.py
index 3f1faa9f..f7ed49e4 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -1502,6 +1502,7 @@ later is required to fix a server side protocol bug.
         if manifest_server.startswith("persistent-"):
             manifest_server = manifest_server[len("persistent-") :]
 
+        # Changes in behavior should update docs/smart-sync.md accordingly.
         try:
             server = xmlrpc.client.Server(manifest_server, transport=transport)
             if opt.smart_sync: