sync: keep smart sync override with -l

Splitting a sync into `repo sync -n` followed by `repo sync -l` should
end up in the same state as a single `repo sync`. With smart sync it
does not always: -n fetches the revisions pinned by the smart sync
manifest and saves it as smart_sync_override.xml, but the following -l
deletes that override and checks out ToT instead, unless the manifest
sets sync-smartsync="true". So `repo sync -s -n` + `repo sync -l` lands
on ToT, while `repo sync -s` lands on the pinned revisions.

Without an explicit -s or -t, -l does not contact the manifest server,
so it cannot choose new pins itself; the only consistent choice is to
keep the override the previous -n left behind. Do that regardless of
the manifest default.

Syncs that choose a manifest themselves still replace or remove the
override as before: any sync without -l, and -l combined with -s, -t,
-m, --superproject-revision or --no-smart-sync. Smart sync stays
non-sticky for regular syncs, and `repo sync -l --no-smart-sync` still
discards the override to check out ToT.

Bug: 569927750
Change-Id: Id06ff88e9f3183fae32e993e86630fc3e8de71a1
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/640965
Commit-Queue: Rahul Yadav <yadavrah@google.com>
Tested-by: Rahul Yadav <yadavrah@google.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>

1 files changed, 14 insertions, 10 deletions

diff --git a/docs/smart-sync.md b/docs/smart-sync.md
index 77f7a9cf9..2da4b90e5 100644
--- a/docs/smart-sync.md
+++ b/docs/smart-sync.md
@@ -138,6 +138,20 @@ copy into `.repo/manifests/smart_sync_override.xml` so users can examine it.
 The next time `repo sync` is run, this file is automatically replaced or removed
 based on the current set of options.
 
+With `-l`/`--local-only` and no explicit `-s`/`--smart-sync` or
+`-t`/`--smart-tag`, repo does not contact the manifest server. Instead, it keeps
+using the existing `smart_sync_override.xml`, if there is one, whether it came
+from an explicit `-s`/`--smart-sync` or from the manifest's `sync-smartsync`
+default. This way, `repo sync -n` followed by `repo sync -l` ends up on the same
+revisions as the equivalent single `repo sync` (e.g. `repo sync -s -n` +
+`repo sync -l` matches `repo sync -s`). Pass `--no-smart-sync` to discard it and
+use the default manifest instead.
+
+`--no-manifest-update` only skips updating the manifest checkout. It does not
+affect Smart Sync: the default Smart Sync from `sync-smartsync` (see below)
+still runs, and an existing `smart_sync_override.xml` is replaced or removed as
+in a regular sync.
+
 ### sync-smartsync (Manifest Attribute)
 
 The manifest can enable Smart Sync by default for all `repo sync` invocations
@@ -158,16 +172,6 @@ sync, as before. Options that specify an explicit target or manifest source
 (such as `-t`/`--smart-tag`, `-m`/`--manifest-name` or
 `--superproject-revision`) will also disable the default Smart Sync behavior.
 
-With `-l`/`--local-only`, the default Smart Sync does not contact the manifest
-server. Instead, repo keeps using the `smart_sync_override.xml` from the last
-Smart Sync, if there is one. Pass `--no-smart-sync` to discard it and use the
-default manifest instead. These options do not change the behavior of an
-explicit `-s`/`--smart-sync`.
-
-`--no-manifest-update` only skips updating the manifest checkout. It does not
-affect Smart Sync: the default Smart Sync still runs, and an existing
-`smart_sync_override.xml` is replaced or removed as in a regular sync.
-
 ### --smart-sync / -s
 
 Explicitly enables Smart Sync. Repo will call